[ 16 April 1997
The Linux Term HOWTO is not being maintained by the author any
more. We both agreed that the term program is nearly obsolete. ]
TERM HOWTO
Patrick Reijnen
[email protected]
v1.2, 15 July 1995
1. Legal Information
1.1. Copyright statement
This document may be distributed freely as a whole in any form and
free of charge. Parts of this document may be distributed, provided
that this copyright message is included and the reader is informed
that this is not the full HOWTO document. Furthermore, there is to be
a pointer as to where the full document can be obtained. Specifically,
it may be included in commercial distributions, without prior consent.
However, I would like to be informed of such usage.
This HOWTO may be translated into any language, whatsoever, provided
that you leave this copyright statement and the disclaimer intact, and
that a notice is appended stating who translated the document.
1.2. DISCLAIMER
While I have tried to include the most correct and up-to-date
information available, I cannot guarantee that usage of the
information in this document does not result in loss of data. I
provide NO WARRANTY about the information in this HOWTO and I cannot
be made liable for any consequences for any damage resulting from
using information in this HOWTO.
2. Introduction
2.1. This Document
This HOWTO attempts to clear up some of the confusion of using TERM,
Michael O'Reilly's remarkable program that allows you to multiplex
your serial line and set up a network connection. By and large, the
documents that come with TERM are quite good, and this HOWTO is not
intended to replace them. The intention of this document is to give
some background on how TERM works and detail the steps in getting some
of the more common networking services working under TERM. It should
be emphasized that this document does not cover everything there is to
know about TERM. After reading it, the TERM manual pages should be
read, since they include information not contained here.
2.2. What is TERM?
TERM is a program, written by Michael O'Reilly (
[email protected])
and maintained by Bill Riemers (
[email protected]), that is run
over a serial line to allow multiple connections to operate
concurrently - i.e. you may be down-load a file via your modem while
working on a (different) remote system via the same modem connection.
TERM can also be used to open up X client windows over a serial
connection. Through the tredir utility and the tudpredir utility TERM
can provide almost all of the ``traditional'' TCP/IP and UDP network
services: mail, news, ftp, telnet, xarchie, etc. In a sense, TERM is
very much like other serial protocols such as SLIP or PPP. TERM's
advantage is that it can be run entirely from user space, requiring no
support from system or network administrators.
Unlike SLIP or PPP, your machine does not have its own IP address. All
incoming traffic must be addressed to your remote host, and it will be
redirected to your local computer by TERM.
3. How TERM works
Before experimenting with TERM it is strongly advised to first read
this complete chapter and the INSTALLATION file provided with the
package. Also take a look at the manual pages linecheck, (term)test
and TERM. This will help you to work easier and faster.
3.1. Nomenclature
I assume you are dialling a system through some sort of terminal
server. I use the terms local and remote to refer to the home and
network connected systems respectively (unless I use them to mean
something else :-).
TERM provides the local machine, which has no network connection, but
is connected, via a serial line, to a remote machine which is in turn
connected to a network with network services. Let us look at how a
machine with a user invokes a program, like ftp or telnet, that
requests a network service. What these programs do is make a system
call requesting network services. The operating system then obtains
these services via its network interface (e.g. it sends and receives
packets over the ethernet). SLIP and PPP do exactly this, by
converting your modem line into a network interface, which is in
principle no different from an ethernet. The downside of this is that
these protocols make the modem-connected machine part of the network,
just like any other machine. This implies all the administrative
burdens associated with being a network node (more actually, since the
modem link must also be administered).
In the absence of a network connection like SLIP or PPP, what does one
typically do? Well, you dial your network connected machine, read your
mail, your news etc; if you need a file, you first transfer it to the
remote machine and then download it to your local machine using kermit
or some other communication program. This is a bit of a pain,
especially since you can only really do one thing at a time that uses
your modem link. The idea behind TERM is basically to automate and
multiplex this process. TERM is invoked on both the local and remote
machines, and the two processes communicate with one another over the
modem line. When you need a network service, you make a request to the
local TERM daemon, which forwards the request to the TERM daemon on
the remote, network-connected, machine. The result is then returned
over the modem line.
To be more concrete, say you want to retrieve a file by ftp. First
you need a version of ftp that can speak to TERM. You invoke this
termftp as you do a regular ftp, say termftp nethost.gov, but this
special version makes its network request to the local TERM daemon
instead of the kernel. The local TERM forwards this request, over the
modem line, to the remote TERM, which opens an ftp connection to
nethost.gov, and transmits the data back over the modem link. TERM is
smart enough to have many different things going on at once; so you
can have several different network sessions using the same modem link,
e.g. you can be logged into another distant host via termtelnet while
the termftp transfer is going on.
If this is too abstract (or unclear) do not worry; the important piece
of information to get out of this section is that there are two copies
of TERM running, one on each end of the modem link.
4. Setting Things Up
4.1. What has to be available
Before you start building and using TERM you have to make sure that
you have built TCP/IP support into the kernel. Furthermore, make sure
that the TCP/IP loopback interface is activated. When this is the case
you can go on with the rest of this section.
4.2. Explanation of concepts
In newer TERM version two new concepts have entered TERM. These two
concepts will be explained in the next two subsections.
4.2.1. Sharing
Starting with version 1.16 the concept of sharing the TERM connection
with other users has entered TERM. This means that when you enable
shared features, other people can use the same TERM connection you are
using, i.e. when you are working on your remote machine via your TERM
connection (say, from your local machine you used trsh to get in)
another person on your local machine can use the same TERM connection
at the same time to ftp a file to his login on your local machine from
an ftp site somewhere in the world.
When you disable shared features (i.e. you execute TERM in private
mode) you and only you (we do not count root :-) can use the TERM
connection.
Of course, you only need to install shared TERM at the end at which
you want to allow people to use the same TERM connection you are
using. So, if other people have a login on your local machine and they
want to use it from somewhere on your remote network you enable shared
features on the remote end of your TERM connection. In this way all
these people can login on your machine at the same time sharing the
same TERM connection with each other and with you. (NOTE: the first
example needed shared features to be enabled at the local end of the
TERM connection).
NOTE for installation as root: When you install TERM as root you have
to create a 'term' group first (before compilation) with no member by
adding the following line in '/etc/group':
term::16:root
or any other unused GID than 16 when 16 is already in use.
After compilation and installation make TERM and its clients SGID
'term':
chgrp term <term_client>
chmod g+s <term_client>
Also any other program that you make TERM-aware must be made SGID
'term'.
4.2.2. Full TERM networking
Starting with TERM version 2.0.0 the statement full TERM networking is
used. When your only connection with the outside world is a TERM
connection, you have a full TERM network and you should build TERM
with full TERM networking. In this case in the shared directory a file
called termnet is placed. This tells TERM that your only connection to
the outside world is via TERM.
When you also have some other type of network connection beside your
TERM connection TERM-aware programs first try to fulfil their job
using this network connection. When this fails TERM is invoked and it
is tried to fulfil the job via the TERM connection. To make this more
clear now an example is given in which TERM-aware telnet is used. This
telnet should work both with and without TERM.
telnet localhost
does not use TERM to connect, but
telnet zeus.cs.kun.nl
will use TERM only if you do not have some other type of network
connection.
Full TERM networking also means to lie about the host name, and say it
is the remote host instead. Furthermore, it causes bind(0) to always
act on the remote host. In essence it makes many programs unusable
when they are not going through TERM, while TERM is running.
Unfortunately, most UDP programs and daemons will not work with TERM
without these nasty tricks.
4.3. Build TERM
When you are lucky, this should just involve a make. Most probably
however, you need to do more. Due to new features in newer versions of
TERM it is now a bit more complicated to create your TERM binary. A
couple of ways can be followed to obtain your binary.
To cover all these ways TERM can be built this section will be split
into three parts:
1. Build TERM, versions 2.0.0 and higher
2. Build TERM, versions 1.16 up to 1.19
3. Build TERM up to version 1.15
4.3.1. Build TERM, versions 2.0.0 and higher
First, make sure you have read the section about 'full TERM
networking' above.
For TERM versions 2.0.0 and higher there are many ways to build the
TERM binary and the clients. All of these can be done both by root and
by ordinary user:
1. Build TERM in private mode without full TERM networking
2. Build TERM in private mode with full TERM networking
3. Build TERM in shared mode without full TERM networking
4. Build TERM in shared mode with full TERM networking
In these versions of TERM a new way for compilation has entered TERM
using the script configure. When configure is run it checks on what
operating system you are trying to install TERM, whether the source
directory is available or not, and if any runtime options are set.
According to the things found configure then creates a Makefile using
Makefile.in which is provided in the TERM package.
Two of the more important options to configure are --root and --user
which state whether TERM will be installed by root or an ordinary
user. Other options can be used to install TERM the way you want (non-
standard paths for example).
1. Build TERM in private mode without full TERM networking.
To build TERM in this way you need to execute the following
commands (both for root and ordinary user):
./configure --root OR --user
make install installman
This builds the binaries and installs these binaries and the manual
pages.
2. Build TERM in private mode with full TERM networking.
To build TERM in this way you need to execute the following
commands (both for root and ordinary user):
./configure --root OR --user
make installnet installman
This builds the binaries and installs these binaries and the manual
pages.
3. Build TERM in shared mode without full TERM networking.
To build TERM in this way you need to execute the following
commands (both for root and ordinary user):
./configure --root OR --user
make share installman
This builds the binaries and installs these binaries and the manual
pages.
4. Build TERM in shared mode with full TERM networking.
To build TERM in this way you need to execute the following
commands (both for root and ordinary user):
./configure --root OR --user
make share installnet installman
This builds the binaries and installs these binaries and the manual
pages.
4.3.2. Build TERM, versions 1.16 up to 1.19
To build these versions of TERM you can now choose one of the
following ways:
1. As an ordinary user, build TERM in private mode
2. As an ordinary user, build TERM in shared mode
3. As root, build TERM in private mode
4. As root, build TERM in shared mode
Below, it will be explained how to enable/disable shared features
during the compilation of TERM.
1. You are an ordinary user (no root access) and you do NOT want to
SHARE the TERM connection with other users.
As a user who does not want to share the TERM connection with other
users you should do the following to build TERM:
make DO=install OS-type
make installman
After this TERM, its clients and the manual pages are built and
installed.
Furthermore, you need to create a directory '$HOME/.term'. This is the
directory in which TERM will look for its 'termrc' file.
2. You are an ordinary user (no root access) and you want to SHARE the
TERM connection with other users.
As a user who wants to share the TERM connection you should do the
following:
make DO=installshare USERSHARE=$HOME/term OS-type
make installman
After this TERM, its clients and the manual pages are built and
installed.
Furthermore, you will have a directory '$HOME/term' (default) with
permissions 'drwxrwxr-x'. In this directory you will find at least the
socket used by TERM for its connection ('tmp/private/socket=').
3. You are root and you do NOT want to SHARE the TERM connection with
other users.
As root who does not want the TERM connection to be shareable you
should do the following to build TERM:
make DO=install OS-type
make installman
After this TERM, its clients and the manual pages are built and
installed.
Furthermore, you now have a directory called '/usr/local/lib/term'
(default) with permissions 'drwxr-xr-x'. In this directory you will at
least find the socket used by TERM for its connection
('tmp/private/socket=').
4. You are root and want to SHARE the TERM connection.
First, make sure you have read the section about 'sharing' above.
As root who wants to share the TERM connection you should do the
following:
make DO=installshare OS-type
make installman
After this TERM, its clients and the manual pages are built and
installed.
Furthermore, you now have a directory called '/usr/local/lib/term'
(default) owned by group TERM and with permissions 'drwxrwxr-x'. In
this directory you will at least find the socket used by TERM for its
connection ('tmp/private/socket=').
4.3.3. Build TERM up to version 1.15
For these versions of TERM building should invoke no more than the
commands
make DO=install OS-type
make installman
You will find TERM, its clients and the manual pages nicely built and
installed and ready for use after this.
Furthermore, you need to create a directory '$HOME/term'. This
directory TERM will use to look for its termrc file.
The only thing you may want to do is change some of the paths in the
Makefile or change some of the compiler flags.
4.4. client.a, libtermnet.a, libtermnet.sa, libtermnet.so
With TERM a library with functions for TERM clients is provided.
Up to version 1.16 this library was called client.a. During
compilation of TERM this library was built and then used during the
compilation of the TERM clients. It was not installed in another
directory.
Starting with version 1.16 the name of the library is changed to
libtermnet.a. Up to version 1.19 this library is created in the TERM
directory and then used during compilation of the TERM clients. It is
not installed in another directory.
Starting with version 2.0.0, beside libtermnet.a also libtermnet.so
and libtermnet.sa (shared library and exported initialized library
data) are created during compilation of the TERM package. During the
installation of all the parts of the package also these three library
files are installed in the directory '/usr/local/lib' (default). Then
a link is made from libtermnet.so.2 to libtermnet.so.2.x.x. Finally,
ldconfig is run to create the necessary links and cache (for use by
the run-time linker, ld.so) to the most recent shared libraries found
in the directories specified on the command line, in the file
'/etc/ld.so.conf', and in the trusted directories ('/usr/lib' and
'/lib'). If the installation is done correctly the three library files
can now be used by TERM clients which are built with dynamic instead
of static libraries. Also, these libraries can now be used to port
your own software to make it TERM aware (see belo! w).
4.5. Setting environment variables
TERM knows a couple of environment variables which can be set by
users. The first three of those that I will explain are
� TERMDIR
� TERMSHARE
� TERMMODE
By setting these variables you can control the way TERM is run.
For TERM versions up to 1.15 only the variable TERMDIR is important
(these versions do not know the shared mode). For these versions
TERMDIR should be set as follows:
setenv TERMDIR $HOME (csh or tcsh)
export TERMDIR=$HOME (bash)
Starting with version 1.16 TERM also knows the variables TERMSHARE and
TERMMODE. With these variables TERM can be told to run in private mode
or in shared mode. I will explain how to set the variables for private
mode and shared mode.
TERMMODE knows the following three values;
� 0 = private
� 1 = system shared
� 2 = user shared
1. Running TERM in private mode can be done setting the variables
TERMDIR and TERMMODE in the following way:
For csh or tcsh
setenv TERMDIR $HOME
setenv TERMMODE 0
For bash
export TERMDIR=$HOME
export TERMMODE=0
2. When you want to use TERM in shared mode there are two ways of
setting the variables:
a. When TERM is installed as a SUID program only TERMMODE has to be
set.
setenv TERMMODE 2 (csh or tcsh)
export TERMMODE=2 (bash)
b. When TERM is installed as a SGID program the variables have to
be set in the following way:
For csh or tcsh
setenv TERMMODE 1
setenv TERMDIR /usr/local/lib/term
setenv TERMSHARE $TERMDIR
For bash
export TERMMODE=1
export TERMDIR=/usr/local/lib/term
export TERMSHARE=$TERMDIR
Setting the variables in this way makes it possible to start old
clients (clients linked to an older version of client.a) in shared
mode.
Starting with version 2.0.0 TERM also knows the variable TERMSERVER.
You need to set this variable when you have multiple modems and you
have more than one connection at a time. To specify which connection
to use, you must start TERM with a server name:
nohup term -v /dev/modem1 Connection1 &
nohup term -v /dev/modem2 Connection2 &
Users should then set the variable TERMSERVER to the connection name
they want to use:
setenv TERMSERVER Connection1 (csh or tcsh)
export TERMSERVER=Connection2 (bash)
4.6. Test TERM
Do a make test (or make termtest for newer versions of TERM) to build
TERM's test daemon. (term)test works by running two copies of TERM on
your system, a should now be able to do a trsh and a tupload (try
tupload ./term /usr/tmp
- you should get a copy of the TERM binary in '/usr/tmp'). The local
TERM's output should show up in 'local.log', the remote's one in
'remote.log'. You can start TERM up with a -d255 flag to enable
debugging output to be written to these files, or enable debugging in
your 'termrc' file.
NOTE: Run test as ./test so as to avoid your system's test.
4.7. TERM and communication programs
Before you can use TERM you must have established a connection via the
modem using a communication program like kermit or seyon. In the
documentation of your communication program you can find what you need
to do to establish the conection with the remote machine.
when you have established the connection with the remote machine and
you want to run TERM you need to suspend or quit your communication
program without closing the connection with the remote machine. This
needs to be done as otherwise the communication program will steal
characters from linecheck or TERM.
Below for some communication programs I will explain how you can make
sure that the connection will stay alive and the communication
programs will not steal characters from linechech or TERM.
4.7.1. Kermit
Starting TERM when you use kermit is easy. At the local kermit prompt
you type suspend. Now you see back your Linux prompt. From this prompt
you can establish your TERM conection.
4.7.2. Seyon
An easy way to start linecheck or TERM when you are using seyon is to
put linecheck and TERM in the Transfer Menu (controlled by the file
'$HOME/.seyon/protocols').
In the file '$HOME/.seyon/protocols' add:
"Line check" "$cd /tmp; linecheck"
"Term" "$term -c off -w 10 -t 150 -s 38400 -l $HOME/tlog"
Then, when you want to execute linecheck or TERM on the local machine,
you can select the Transfer Menu, either the "Line check" or the
"Term" item, and Go.
Of course, you can also use the shell command button, and type
'linecheck' or 'term' in the pop-up dialog box. This also does
automatic redirection of input and output.
4.8. Make a Transparent Link
Presumably, you can establish a modem connection between your local
and remote hosts. Typically, you are dialling into some kind of
terminal server and connecting to your remote host from there. You are
also using some kind of terminal software, such as kermit or seyon to
talk to your modem (the examples in this document will use kermit,
since that is what its author uses). If you are having trouble with
your modem, or your terminal software, take a look at the Serial-
HOWTO; that should help you out.
Having established your link, you want to make it as transparent as
possible. Check the commands on the terminal server (help or ? will
usually get you started). Go for the 8 bit options whenever possible.
This may mean changing the way you log in to a system, e.g. if the
server uses rlogin, you may have to use it and give it the -8 flag to
make it transparent. Especially watch out for xon/xoff flow control.
You do not want that. Try to enable rts/cts (hardware) flow control.
You may need to check your modem documentation to learn how to
configure it to do 8-bit rts/cts communications.
4.9. Run linecheck
WARNING: In some of the documents the command line options for
linecheck are mentioned in an incorrect order. I have checked this and
found the order of options mentioned below to be the correct ones.
NOTE: Starting with TERM version 2.3.0 linecheck no longer needs to
have the name of a log-file on its command line. It will write its
output to the file 'linecheck.log' in the directory you start
linecheck in.
Linecheck is a program that is supplied with TERM. It checks the
transparency of a link, providing configuration information that TERM
needs to run correctly. linecheck will send each of the 256 possible
eight bit characters over the link and verify that each was
transmitted successfully. TERM needs to be configured to deal with
characters that cannot be transmitted over the link, and linecheck
determines what characters these are. You use linecheck after you have
established as transparent a modem link as possible. To run linecheck,
do the following
1. On the remote system run
linecheck linecheck.log
2. Escape back to your local system and suspend your communication
program (see above)
3. On the local system run
linecheck linecheck.log > /dev/modem < /dev/modem
When linecheck is done, you will find a set of numbers at the bottom
of the 'linecheck.log' files. These should be escaped in the termrc at
the other end of the link. For example, in my system my local
'linecheck.log' said nothing and my remote 'linecheck.log' said to
escape 29 and 157. Therefore, my local I have to also ignore it at
the other; so, in this example, I shall have to ignore 29 and 157 in
my remote system.
If linecheck hangs, try using
linecheck linecheck.log 17 19
on the remote system and
linecheck linecheck.log 17 19 > /dev/modem < /dev/modem
on the local system. This will escape your xon/xoff (flow control)
characters, which will hang your line if you have got software flow
control. If this solves the hanging problems, you will want to escape
/ignore 17/19 in both 'termrc's'. If your terminal server has other
characters that will shut it down, try running linecheck with those
characters escaped, as above. You can spot these characters if
linecheck hangs. If this is the case, kill it, then look in the log-
files. The last characters transmitted are likely to be the culprits.
Try it again with these characters escaped.
In summary, my local termrc has the lines
escape 29
escape 157
and my remote termrc has the lines
ignore 29
ignore 157
since my remote 'linecheck.log' said to escape 29 and 157.
4.10. Try Running TERM
Log into the remote system, making the link as transparent as possible
(if you have not already done so). Fire up TERM at the remote end. I
use the following:
exec term -r -l $HOME/tlog -s 38400 -c off -w 10 -t 150.
Let us run down each option one by one (note that I could just as
easily have put these options in my termrc. I did it this way because
it saves editing a file while getting TERM set up).
exec means to destroy your current shell, running the given program in
its place. I exec things because I do not intend to use my login shell
again; so it is just wasting memory. If you are debugging the link and
can reliably kill the remote TERM, you might not want to do an exec.
The -r option is needed at exactly one end. TERM will then see this
end as the remote end of the connection (Note that TERM's remote end
can thus be your local machine). If you do not use this option at one
end TERM clients will spontaneously crash.
-l $HOME/tlog. This logs errors to the file tlog in my home directory.
Very useful for debugging. No reason not to do this.
-s 38400 : I have got a 14400 baud modem, with compression. For
optimal compression ratios, I want to be able to push bits down the
pipe as fast as possible. For a slower modem, you should use something
lower. Note that if you have a slower machine with 16450 uart on your
serial port, high baud rates can cause data loss by overloading the
chip on your serial port. TERM will recover from this, but if you see
a lot of error messages in your log file, (or get overrun warnings
from linux kernel versions 0.99pl15 and up) you again might want to
lower this number.
-c off : This turns data compression off. I have got a compressing
modem, and I do not want to compress things twice.
-w 10 -t 150 : Again, these are options to optimize my fast modem
link. I have set my window to 10 and my timeout to 150. This is
according to the recommendation in the term_setup man page.
Escape back to your local machine and suspend your communication
program (see above). You do not want it running while TERM is running,
because it will fight with TERM over the serial port. If you can
convince your modem to not hang up when you exit your communication
program (when it toggles DTR), you could just exit the program at this
point.
Now run TERM locally. I use:
term -c off -l $HOME/tlog -s 38400 -w 10 -t 150 < /dev/modem > /dev/modem &
I need to tell TERM where the modem is; so I point both standard input
and output at '/dev/modem' (that is what the < and > do). I also run
it in the background; so I can use this screen for something else if I
want to.
TERM should work now :-). Try a trsh, and see what happens. If you
hang, or your link seems slow, take a look at your 'tlog' at each end.
Are you getting timeouts or error messages? If so, then you have
configured something incorrectly. Try again (after you have finished
reading this :-). Note that the connection will not seem blazingly
fast, especially if you are using compression - it will be a little
jumpy. The real speed comes in during file transfer and the like.
4.11. Terminate your TERM connection
Most certainly, after you have done a lot of work using TERM, you want
to finish your work and bring your TERM connection down. For this to
be realized there are four ways:
1. Kill the TERM programs at both sides of the connection. This is the
least recommended way of terminating your connection.
2. A better way is to execute the following command locally:
echo '00000' > /dev/modem
This will nicely terminate your TERM connection. It will work for all
version of TERM. Make sure that the sequence of zeros contains at
least five zeros.
3. In the termrc of TERM versions 2.0.0 and higher you can now enter a
statement called terminate '<some string>'. This sets a string that
will cause TERM to exit ('00000' by default). It must be at least
five characters long, to avoid accidently terminations.
4. Starting with version 1.14 there is the program tshutdown (actually
for version 1.14 it is available as a patch, for newer versions it
is in the package). Executing tshutdown nicely terminates your TERM
connection.
4.12. Removing TERM from your partition
Ok, you asked for this. As some of you want to get rid of TERM I here
present you the steps to be done in removing TERM. In the process of
removing TERM you have to fulfil the following steps:
� Removing directories with their contents. Depending on how you
installed TERM, one or more of the following directorieswill exist
on your machine:
$HOME/.term/termrc
$HOME/.term/termrc.<server>
$HOME/term/termrc
$HOME/term/termrc.<server>
/usr/local/lib/term/termrc
/usr/local/lib/term/termrc.<server>
/etc/termrc
/etc/termrc.<server>
These directories can be removed together with their contents. Use
'/bin/rm -rf' to get this done.
� The group 'term'. For some of the ways of installation you had to
create a group 'term'. Check the file '/etc/group' for the 'term'
entry. When it exists you can remove the entry.
� The TERM-package and TERM-aware executables. This is probably the
hardest part in removing TERM. For the executables coming with the
TERM-package you have to look in the directory '/usr/local/bin' or
the directory '$HOME/bin'.
With executables you made TERM-aware yourself I cannot help you.
You need to know what executables you made TERM-aware in order to
know what executables you have to remove. Do not forget
configuration, default and other files coming with some of these
executables.
� Library files. To remove these you best can execute the following
commands:
cd /
find . -name libtermnet* -exec /bin/rm {}
This will find and remove the library files.
� Include file. Also for this one the easiest way is to execute the
following two commands:
cd /
find . -name termnet.h -exec /bin/rm {}
This will remove the include file.
� Manual pages. When you have installed the TERM manual pages you can
now find them back in one of the following directories:
/usr/local/man/man1
/usr/local/man/cat1
$HOME/man/man1
$HOME/man/cat1
At least you have to check for the following manual pages: term,
term_clients, term_setup, tdownload, linecheck, trdate, trdated,
termrc, termtest, tmon, tredir, trsh, tshutdown, tudpredir, tupload,
txconnand finally tiptest.
� Temporary user directory. This is de directory '/usr/tmp/private'
and its contents.
After this exercise you can be quite sure that you have removed
everything related to TERM.
4.13. Optimizing your connection
Once you have got TERM running, you might want to try to get things
optimized. A good way to measure the speed of your link is to run tmon
in one window while up/downloading a file in another. Try both (big)
text files and compressed files; the plain text should go a factor of
two-ish faster than the compressed files. The parameters you want to
fiddle with are baud rate (-s), compression (-c), windows (-w),
timeout (-t) and retrain (-A).
Watch out with the retrain parameter. With TERM version 1.19 I got a
performance decrease of 80% to 90% compared to running TERM without
the retrain parameter. It is not clear if this is a bug in TERM
version 1.19 and if this problem exists only with TERM version 1.19.
Baudrate: the maximum number of bits per second TERM will try to send
over the serial link. TERM will avoid sending characters at a higher
data rate than this. The default is to use the speed of your
computer's serial port, but be warned that this may be too high if
your modem runs at a lower rate over the phone line. The baud rate
option is intended for systems that buffer output to the modem. During
setup and tuning it is better to use a small baud rate rather than one
which is too large. For high speed links (> 38400), making it
unlimited is probably advantageous. This is achieved by using the
value 'off'. TERM will then rely solely on your kernel to do flow
control.
Compression: you want this on if you do not have a compressing modem.
If you do have such a modem, turn compression off, otherwise you will
be compressing things twice, which typically increases the amount of
data transmitted. Compressing modems are those that use the MNP-5 or
V42.bis protocols. Check your modem documentation and the message when
your modem connects.
Windows: this is the number of chunks of data, or packets, that TERM
will let go over the line before it gets an acknowledgment (or ack)
from the remote TERM. For fast modems, increasing this can be a win;
for slower links this can overwhelm the remote end.
Timeout: the time TERM will wait for an ack. If you have increased
windows, and you are getting timeouts in your log-file, try increasing
this.
For 14400/V42.bis, I use -c off -w 10 -t 150. I get around 1700 cps on
compressed files and 3500 cps on ASCII files using tupload.
4.14. Troubleshooting
In this section some thoughts are given about what to check when you
have problems executing TERM or one of its clients.
� Did you clean up the TERM directory structure? With newer versions
of TERM the structure of the directory tree under
'/usr/local/lib/term' has changed a couple of times. If you are not
aware of this, it can cause all kinds of error messages. The best
thing to do is to delete the directory tree under
'/usr/local/lib/term' (save your 'termrc') and then install your
new TERM version. This way, you avoid the struggle with a messed up
directory tree.
� Did you remove old sockets? When you update your TERM version
remove all the sockets (called 'socket=') created by TERM. No doing
this can cause strange problems. To find out what socket TERM is
listening to you can use the "netstat" program.
� TERM does not compile correct on sunOS 4.1.3? You have configured
TERM with './configure --user'. During compilation you are getting
a assembler error on a unknown '-k' flag. The reason of this error
is unknown. The solution to this error is to configure TERM with
static libraries. So, you have to do './configure --user --static'
and then continue with the compilation process the way you normally
do. Now TERM should compile correct.
� termtest is presenting you the error: 'Term: failed to connect to
term socket '/root/.term/sockettest''? When termtest runs it
expects the executable 'term' to be in the same directory as
termtest. When you do a 'make install' prior to running termtest,
the TERM binary is moved to '/usr/local/bin' (or some other bin
directory).
The workaround for this is to link the binary to the source
directory:
ln -s /usr/local/bin/term /usr/src/term-<version_number>/term
� Are you running the right binary? TERM has been updated quite a
lot, and many systems have different versions of the programs
floating around. Make sure you are using the right version. Note
that this applies to linecheck too. You can use bash's type -a or
the whereis command to find which program is being run. TERM
versions after 1.11 should print out their version number when they
start up. (Although version 1.14 claims to be 1.12. Sigh.)
� Do you have the right 'termrc' in the right place? Depending on the
version of TERM you are running and the way you installed TERM
(being root or user) this file has to be in one of the following
directories:
$HOME/.term/termrc
$HOME/.term/termrc.<server>
$HOME/term/termrc
$HOME/term/termrc.<server>
/usr/local/lib/term/termrc
/usr/local/lib/term/termrc.<server>
/etc/termrc
/etc/termrc.<server>
Some systems have pre-installed 'termrc' files; make sure they are
gone before you set things up. If you are running things as root,
lookout for '/.term'. TERM creates files (sockets actually) while it
is running; so it has its own directory, (note, there is no leading
dot in 'termrc'!).
� Does TERM find its 'termrc' file? when you start up TERM at both
sides, you should see messages like the one below:
Term version: 2.2.9
Reading file: /usr/local/lib/term/termrc
Using shared mode.
When the second line is missing TERM cannot find its 'termrc' file and
you know that something is gone wrong during the installation (unless
you are not using a 'termrc' file and enter all the options to the
command line :-). Check the place and the permissions of the 'termrc'
file on the site TERM cannot find its 'termrc' file.
� Do the entries in the 'termrc' file have the correct syntax and
spelling? A known problem is that people who need to escape and
ignore several characters enter them like this in the 'termrc'
file:
escape 1,4,30,255
ignore 1,4,30,255
Although TERM does NOT like this it will not complain. It only escapes
or ignores the first character presented to the escape or ignore
statement. The others characters are silently handled as not being
there.
When you have to escape or ignore several characters you have to put
them on separate lines in your 'termrc' file, each line starting with
the keyword escape or ignore. Only when you have to escape or ignore a
range of characters you can do it the following way:
escape 16-19 # escape characters 16, 17, 18, 19
escape 23 # 23
escpae 255 # and 255
ignore 16-19 # ignore characters 16, 17, 18, 19
ignore 23 # 23
ignore 255 # and 255
� Is you 'term' or '.term' directory mounted with NFS? If your 'term'
or '.term' directory is mounted with NFS you need to set the flag
-DTERM_NFS_DIR in the CFLAGS line of the Makefile. Alas, for the
author this flag causes a compile error when TERM 1.19 is compiled
on a machine running sunOS 4.*.
� Are all files and directories owned by the correct user and group
and do they have the correct permissions? This should be no
problems as these permissions are set during the installation
phase. However, when you port your own programs to TERM you must be
aware of this. Also when you change the mode TERM is working in
(i.e. from private mode to shared mode) file and directory
ownerships and permissions have to be adapted.
� You are getting the error gethostbyname: <hostname>: Non-
authoritative `host not found', or, server failed
To solve this you have to check the following things:
1. Is the file '/etc/hosts' configured correctly? <hostname> is not
the name of your host (old SLS releases and some old and new
Slackware releases are shipped with hostname 'darkstar' for
example). Change this in this file. It must at least contain a
line like below (the format is described above it):
# Local Hosts Format:
# IP_NUMBER HOSTNAME ALIASES
#
# Here is the name of your host, first, followed by any aliases
127.0.0.1 localhost linuxpc.domain linuxpc
When your only connection to the outside world is by TERM the line
above is the only one that may appear in the file '/etc/hosts'. Do
not put actual addresses of frequently visited destinations in
'/etc/hosts'. TERM does not like these to be in '/etc/hosts' and it
will hang on them.
2. Are your '/etc/rc*' and '/etc/resolv.conf' files world readable
(chmod ugo+r)?
3. Last, make sure that you have installed the TCP/IP loopback-
interface on your machine. You can check for loopback by running
the command 'ifconfig'. When you have installed the loopback-
interface you will at least get something like:
lo Link encap:Local Loopback
inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.255.255.0
UP BROADCAST LOOPBACK RUNNING MTU:2000 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0
TX packets:4984 errors:0 dropped:0 overruns:0
on your screen. During boot time you can furthemore check which
protocols are in use. On my machine a line like the one below then
appears:
IP Protocols: ICMP, UDP, TCP
For the installation of TCP/IP and the loopback-interface, please
read to the NET-HOWTO.
� You are getting all kinds of 'timed out' messages in your TERM log
files? This means that your TERM connection is not optimized. A
small number of these messages every now and then is not a problem.
These are most certainly due to temporal factors influencing the
physical connection between your local and remote hosts.
When you get a lot of these messages all the time your connection
will slow down considerably. You have to fiddle with the parameters
mentioned in the section 'Optimizing your connection' above. Alas,
this part of the installation is a process of trial and error. No
hard rules can be given about the numbers to be presented to the
various parameters as many factors have an influence on the
connection. These factors differ between the connections and even
in time.
� Normal FTP with redirected ports does not work for you? Alas, it is
a known problem that redirection of the ports needed by FTP (20 and
21) does not give you a working FTP. The only solution is to get a
TERM-aware ftp or ncftp version. Alas, also some TERM-aware ftp
versions seem not to work.
5. TERM clients
TERM provides several default clients. They include trsh, tmon,
tupload, tredir, txconn and in newer versions trdate, trdated.
Furthermore, starting with version 2.0.0 tudpredir is available and
from version 2.1.0 tdownload is available. This section will deal with
trsh, tmon, tupload, tdownload, trdate and trdated. The others each
have their own section. No TERM client will work until you have
established a TERM link.
tmon is a simple utility to monitor the statistics of your link. It
prints a time histogram of characters transmitted and received. It is
invoked simply as tmon. Since around version 1.11, tmon has had a bug
that causes some information to be garbled (??).
trsh is similar to rsh. Without arguments, it spawns an interactive
shell on the remote system (i.e. it logs you in). trsh is one of the
primary means of accessing the remote end of the link via TERM. If
given an argument, trsh executes that argument as a command on the
remote system. For example
trsh ls
would give you a listing of the files in your home directory on the
remote system.
tupload will transfer a file, given as its first argument, from local
to remote. By default, the files will be put in the same directory
that you invoked TERM from at the other side. To put files in another
directory, give their names as a second argument to tupload. For
example, if I want to put a copy of the file 'term114.tar.gz' in
'/usr/tmp' on the remote system, I would type
tupload term114.tar.gz /usr/tmp
When you use tupload you can use wild cards like in 'tupload a.*'. The
shell expands the wild card and tupload is called as 'tupload a.1 a.2
......'.
tdownload will transfer a file, given as its first argument, from
remote to local. By default, the files will be put in the same
directory that you invoked TERM from at the local side. To put files
in another directory, give their names as a second argument to
tdownload. For example, if I want to put a copy of the file
'term114.tar.gz' in '/usr/tmp' on the local system, I would type
tdownload term114.tar.gz /usr/tmp
When you use tdownload you cannot use wild cards like in 'tdownload
a.*'. Reason for this is that the remote directory is not available to
your local shell when you use tdownload; so your local shell cannot
expand the wild cards.
trdate is a time setting utility. It reads the time on the remote
machine and sets the local clock to the remote time. It must be run as
root.
trdated is the daemon version of trdate. When it is started in
'rc.local' it is run as daemon in which case it updates the time every
5 minutes (default). Even when there is no TERM connection, this
daemon will start up when set in the rc.local. Once a TERM connection
is created it starts updating the time.
6. X and TERM
TERM allows users to open up X windows on the local machine from
clients that are running on a machine on the network. This is done by
using the txconn client. txconn is executed on the remote, network-
connected machine; it is invoked simply as txconn. It goes into the
background and returns a number on the standard output; this number is
the display number that clients should use to access the X server on
the local machine. An example should make this clear. I am logged in,
via trsh, to my remote TERM host, named foo. On foo, I do the
following
foo$ txconn
Xconn bound to screen 10
:10
foo$
Now, on any host that I wish to run an X client on, that is to display
on my local machine's X server, I do
setenv DISPLAY foo:10
(for bash you should use export DISPLAY=foo:10). In some cases it can
furthermore be necessary to do a
xhost + foo
or even a
xhost +
on your local machine. Now when I start the client, it will try to
connect to screen 10 on machine foo, but txconn is listening to this
screen, and will forward all X protocol packets via TERM to the X
server on the local host - i.e. the window will open up on your local
machine.
It is possible to go the other way - run a client on your local
machine and have it open up a window on a remote machine on the
network; however we will defer explaining this until after we have
discussed tredir.
The X protocol is not very efficient; it wastes some bandwidth. This
is usually not a problem over an ethernet, but can be murder over a
modem. X11R6 is supposed to introduce a low bandwidth version of the X
protocol, LBX. If however you are using X11R5 you can use a utility
named sxpc which compresses the X protocol, improving response over
serial lines. Sxpc includes a write-up on how to get it working with
TERM, and is recommended. The sxpc package also explains how to use
xauth; so it is doubly recommended.
7. tredir
tredir is one of TERM's most powerful utilities, allowing most
important network services to be performed over a TERM link. Before we
explain how to use tredir, it is necessary to give some background on
network services. We have talked about network services before, but we
have not said exactly what they are. Services are just that - services
that are provided by the network. Examples of services include telnet,
which provides logins between machines, the File Transfer Protocol,
ftp, which transfers files between machines, and smtp, the Simple Mail
Transfer Protocol, which is used whenever you send electronic mail.
Each network service has a port number associated with it. The
mapping of port numbers to services is given in the file internet-
connected machines.
How are these services invoked? Each networked machine runs a daemon
called inetd, which listens for attempts to connect to the network
ports. These requests can come from either the network or the local
machine. A network service is obtained by connecting to a particular
inetd port. When a network request is made, inetd knows exactly which
service is involved by the port number the request is made on. If
inetd is configured to do so, it provides the relevant service to the
requesting connection. inetd's configuration is given by the file
'/etc/inetd.conf', which has a list of the services that inetd
provides. For more information, see the man pages for inetd and
inetd.conf.
You can communicate directly with network services by using telnet
(n.b. not termtelnet). For example, to talk to the sendmail, (or smtp)
daemon on machine machine_name, you can do a telnet machine_name smtp,
or telnet machine_name 25, (since 25 is the number assigned to smtp in
'/etc/services'). You should get a polite greeting from the daemon on
the remote machine. This is a very useful trick for debugging network
problems and checking ports redirected with tredir (see below).
Tredir works very much like inetd. It runs in the background as a
daemon, listening to the network ports, waiting for a request. When a
request for a service is made, instead of providing that service, as
inetd does, tredir forwards the request over the TERM link to the
remote TERM, which makes the request over the network, returning the
result back over the link to the local client. Tredir can forward the
request to any machine on the network, but by default sends it to the
machine at the other end of the TERM link. Tredir redirects TCP
(Transmission Control Protocol) network services over the TERM link.
The common command format of tredir is:
tredir [this_computer:]port [that_computer:]port
An example should make this clear. Let us redirect a local port to the
telnet port on the remote machine. To do this we would do
tredir 2023 23
Now, anyone who connects to port 2023 on the local machine will be
redirected to port 23 (telnet) on the remote machine. Here is an
example session; the local machine is mymachine.modem.home and the
remote machine is netsun.
$ tredir 2023 23
Redirecting 2023 to 23
$ telnet localhost 2023
Trying 127.0.0.1...
Connected to mymachine.modem.home
Escape character is '^]'.
SunOS UNIX (netsun)
login:
This example is actually quite useful. If I were instead to do the
tredir on netsun. I could then telnet in to mymachine from the network
simply by connecting to the redirected port on the networked machine
(using telnet) - i.e. telnet netsun 2023.
The general principle in using tredir is to redirect the desired
service to a machine on the network. Our next example will allow us to
read news on the local machine over our TERM link from a news server
on the network. News is provided by the nntp service, port number 119.
All decent news readers allow you to specify what port number they
will use, either via a configuration file or an environment variable.
Let us specify this local port to be 2119. Now, let us say that our
news server is news.domain.org. We will redirect port 2119 to port 119
on news.domain.org; we will then tell our news reading software that
the nntp server is located at port 2119 on the local host. Since this
will depend on the news reader that you use, I will just test the link
with telnet instead of firing up a news reader:
$ tredir 2119 news.domain.org:119
Redirecting 2119 to news.domain.org:119
$ telnet localhost 2119
Trying 127.0.0.1...
Connected to mymachine.modem.home.
Escape character is '^]'.
200 news.domain.org InterNetNews NNRP server INN 1.4 07-Dec-41 ready
(posting ok).
If you can get this far, all you have to do is configure your news
reader to be able to read news via TERM. (n.b., if you read news like
this, be sure that in all your posts you set a Reply-To: header to an
network email address that you can be reached at, otherwise people who
want to get in touch with you will be sending mail to whatever (wrong)
data your news reader puts in the From: header).
7.1. tredir can bite!
The astute reader, after reading the last example will be wondering
why port 2119 was redirected to port 119 - since news readers default
to port 119, why could I not do a tredir 119 news.domain.org:119 and
skip the news reader configuration? The answer is that all ports
numbered less than 1024 are ``reserved ports'', and only the superuser
can listen to them. If one is willing to take a security risk and make
tredir an SUID program, or run tredir as root, then one can redirect
reserved ports and avoid the hassle of renaming services.
Another problem with using reserved ports is that inetd is often
already listening to these ports, and only one program at a time can
listen to a port. In order to use such a port, you must change port
you want to redirect. This is most easily done by commenting out the
line with the offending service by putting a # character at the
beginning of the line. The superuser must then send inetd a HUP signal
(kill -1 inetd-pid) to get it to reread its configuration.
7.2. Stupid tredir tricks
In this section we will describe some of the more common uses for
tredir. We have already described how to redirect nntp and telnet
services; here we will give some more complicated examples.
7.2.1. X windows
In a previous section, we described how to get an X client running on
the network to open a window on your home machine using txconn. The
same technique could be used on your home machine to display a client
on the machine at the remote end of your TERM link. But how does one
display an X client on a network machine that is not the remote end?
The answer lies in knowing that X uses a particular network service
just like the other programs we have been discussing. An X server
listens for a network request on a port whose number is given by the
formula port = 6000 + display number, e.g. an X server managing
screen 0 on a machine would listen to port 6000, if it were managing
screen 2, it would listen to port 6002. When you set your DISPLAY
environment variable to xmachine:n, your X clients will try to connect
to port 6000 +n on xmachine.
We can use this to trick X clients on your local machine to open up
windows on remote displays. Let us say I want to open up an xterm,
running on my local machine, on display 0 of machine xmachine, which
is running some place on the network. I first pick a local display
number, say 2 (do not use 0, since that is what your local X server
will be using). I will map this display to display 0 on xmachine. In
terms of ports, this means I want to redirect the local port 6002 to
the remote port 6000. I do the following
$ tredir 6002 xmachine:6000
$ setenv DISPLAY localhost:2
$ xterm
This should open up an xterm on machine xmachine. Note that I set the
DISPLAY to localhost:2. This is because X clients will sometimes use
unix domain sockets instead of internet domain sockets, at their own
option, when connecting to a local display, if DISPLAY is set to :2.
localhost:2 says to use a TCP connection.
Note that as far as xmachine is concerned, the X request is coming
from the machine on the remote end of your TERM link (remotemachine) -
so if you need to authorize the connection, you should either do an
xhost + remotemachine on xmachine or use xauth to update the
'.Xauthority' file on your local machine for display number 2, using
the key from xmachine.
Again, to speed up X connections, you can use the program sxpc, which
includes an explanation of how to use tredir to establish the link and
authorize it using xauth.
7.2.2. Mail with TERM
Well, you asked for it. Electronic mail has the justifiable reputation
of being one of the most difficult things to get working right on a
UNIX system. To really get TERM working correctly with mail means that
you have to understand how mail works, which is beyond the scope of
this document. To learn more about mail, you should consult a book on
UNIX system administration and/or the comp.mail.misc FAQ, available
for anonymous ftp on rtfm.mit.edu:pub/usenet/comp.mail.misc. There are
also currently two packages available for anonymous ftp on
sunsite.unc.edu that will help you get mail running under TERM - they
are term.mailerd+smail by Byron A. Jeff and the BCRMailHandlerXXX by
Bill C. Riemers.
That being said, we will give a thumbnail description of how mail
works. There are two parts to getting mail running, sending messages
and receiving messages. We will begin with sending messages from your
local box to the network.
There are two classes of mail programs. The first is the mail user
agent (MUA). MUA's help you read, compose and send messages. Examples
of MUA's are elm, pine, Mail and vm. MUA's do not really do any
networking; they just put the messages together - the real work of
sending mail is done by the second class of mail programs, the mail
transfer agents (MTA's). These are invoked by the MUA's. They take the
message, decide where to send it by looking at the address, and then
actually deliver it over the network.
The two most common MTA's on Linux systems are sendmail and smail. The
basic idea is to get your MTA to connect to another MTA running on a
machine on the net that will know what to do with your message. This
is done by redirecting a local port to the smtp port on the net
machine. You then have to tell you MTA to take any message it does not
know what to do with, and send it out over the redirected port on your
local machine to the MTA on the remote machine, which will then route
your message to its correct destination.
How do we do this using smail? We first redirect a port to the smtp
port on the network mail machine (mailhost):
tredir XXXX mailhost:25
here XXXX is the port number that the smail on the localhost will
connect to (note that I have to give this port a name in my
'/etc/services' to get smail to recognize it). Smail has several
configuration files that usually live in '/usr/local/lib/smail'. The
ones we care about are that I am assuming you have already got smail
configured correctly for local mail - delivery to files and pipes and
such things. Again, consult the documentation if you have not.
In the file 'config', we put the following definition:
smart_path=localhost
localhost is the machine that smail connects to when it does not know
what to do with a message.
In 'routers' we put
smart_host:
driver=smarthost,
transport=termsmtp;
path = localhost
In 'transports' we put
termsmtp: driver=tcpsmtp,
inet,
return_path,
remove_header="From",
append_header="From: YOUR_NET_ADDRESS",
-received,
-max_addrs, -max_chars;
service=YOUR_SMTP_SERVICE,
In the above, the header lines change the From header in all your
outgoing mail to the address, YOUR_NET_ADDRESS, which is the network
address you want mail sent to. If more than one user is going to be
using your TERM link, you will have to do something more fancy, like
keep a database of local user's network addresses and insert these in
the From: headers.
The service line is the name of the local port number that you have
redirected to the smtp port on the network connected machine. In my
version of smail, I cannot just set this to a number, I have to set it
to a name, like ``foo'', and then define ``foo'' in my '/etc/services'
to be the number of my redirected port. If you use a SUID tredir and
just redirect the smtp port (25), you do not need to define this.
This should be enough to get you going. If you decide to use sendmail,
the principles are the same but the details differ. Ronald Florence
(
[email protected]) told me that the stock Sun sendmail will not send
multiple queued messages over a redirected port; BSD sendmail 8.6.9
works fine. He made the following changes to '/etc/sendmail.cf' to
get it working with TERM. In his case, the default sendmail port (25)
is used for SMTP traffic over a local ethernet so Internet mail is
forwarded to a redirected TCP port.
#
#Create the termsmtp mailer, which sends mail via a re-directed TCP port
#
Mtermsmtp,P=[TCP], F=mDFMuCXe, S=22, R=22, A=TCP $h PORTNUMBER
Here, PORTNUMBER is the number of the redirected port on the local
machine. This should be an unused port over 2000. We next tell
sendmail which machine to connect to, and set termsmtp as the default
mailer.
#
# major relay mailer
#
DMtermsmtp
#
# major relay host: use the $M mailer to send mail to other domains
#
DR HOSTNAME
CR HOSTNAME
Here HOSTNAME is the name of your local host (does localhost work?).
The last entry goes under Rule 0 to forward Internet mail.
# Pass other valid names up the ladder to our forwarder
R$*<@$*.$+>$* $#$M $@$R $:$1<@$2.$3>$4
[email protected]
When the TERM connection is established to the Internet host, run the
following commands on the local machine.
tredir PORTNUMBER internet.host:25
/usr/lib/sendmail -q
We now turn to receiving electronic mail using TERM. We will assume
that mail is sent to your account on the network machine mailhost. The
simplest solution is to just use trsh or termtelnet to log on to
mailhost and read your mail on there. However, it is also possible to
have your mail automatically downloaded to your local machine. One way
to do this is to use the Post Office Protocol, (POP). POP was designed
for exactly this purpose: to deliver mail to machines that have
intermittent network connections. To use POP, you must have a POP
server installed on mailhost. Assuming that you do, you can then use a
POP client to download your mail every few minutes. This is done, as
you might expect, using tredir. The POP service is 110 (note that
there is an older protocol, POP-2, which uses port 109; in this
document we describe POP-3, which is the latest version of POP). There
are several POP clients available. One, written in the script language
perl is pop-perl-1.X, written by William Perry and maintained by
myself - it can be found on sunsite.unc.edu:pub/Linux/system/Mail.
To use POP, you redirect a local port to port 110 on mailhost and
configure your client to retrieve your mail from localhost using the
local port. As an example, we will assume that there is a POP server
running on mailhost. We will redirect the local port 2110, and fire up
the pop-perl client:
$ tredir 2110 mailhost:110
Redirecting 2110 to mailhost:110
$ pop
Username: bill
Password: <enter your password for mailhost>
Pop Host: name of local
Pop Port: 2110
Starting popmail daemon for bill
If you do not have a POP server available, the BCRMailHandler package
has a program to download your mail over a TERM link to your local
machine. I have not used it, but anyone who has is welcome to comment.
You can also use the term.mailerd+smail package for this purpose.
Alas, both BCRMailHandler and the term.mailerd.smail package do not
work anymore with TERM versions 2.0.0 and higher.
8. tudpredir
tudpredir is similar to tredir when you look at what these programs do
and how they are executed. The big difference between the two programs
is that tredir is used to redirect TCP network services while
tudpredir redirects UDP (User Datagram Protocol) network services over
the TERM link. One more important difference between the two programs
is that tredir becomes a background daemon once it has successfully
established the local port, while tudpredir commands must be placed in
the background manually.
The common command format of tudpredir is:
tudpredir [this_computer:]port [that_computer:]port
9. Automating Things
Now that you know how to get all your network services over TERM, it
would be nice to set things up in such a way that your link is set up
and configured automatically. There are basically an infinite number
of ways of doing so, depending on what communication program you use
and how you log in to your remote system.
One program that I have not used, but I have heard is quite nice, is
fet: a front end for TERM. It is designed to log you into a remote
system and fire up TERM and all your tredir's. Any comments on fet
would be most welcome.
I shall now give an example of a set of commands that use kermit to
log into the remote system and then performs all of the TERM
initializations. Obviously, if you use these examples, you will have
to modify them for your own login procedures.
The command which is actually invoked is the shell script 'knet',
given by:
#!/bin/sh
/usr/bin/kermit -y $HOME/.kerm_term > $HOME/klog < /dev/null 2>& 1
exec $HOME/bin/tstart >> $HOME/klog 2>& 1
The script '.kerm_term' is given by:
pause 2
# The number you want to dial
output atdtXXXXXXX \13
# Login to the terminal server
input 145 {name: }
output MYNAME \13
input 3 {word: }
output MYPASSWORD \13
input 5 {xyplex>}
# Make the line transparent
output term telnet-t \13
output term stopb 1 \13
# Connect to the remote host
output telnet remotehost.somedomain.org \13
input 10 {ogin: }
output MYOTHERNAME \13
input 3 word:
output MYOTHERPASSWORD \13
pause 5
# Fire up term on the remote host
output exec term -s 38400 -l $HOME/tlog -w 10 -t 150 \13
! /usr/bin/term -r -l $HOME/tlog -s 38400 -c off -w 10 -t 150 < /dev/modem > /dev/modem &
# Open other clients here
suspend
!killall -KILL term
and finally, the script 'tstart' which fires up the TERM clients is
given by
#!/bin/sh
#
# This lets mail get out, can read news here, can pick up my mail here
#
/usr/local/bin/tredir 2025 25 2119 newshost:119 2110 pophost:110
#
# So I can open up Xwindows here
#
/usr/local/bin/trsh -s txconn
#
# So I will receive mail....
#
/usr/local/bin/pop
#
# Clean out the queue, in case of boo-boos
#
/usr/bin/runq
#
# Done now
#
echo ^G^G > /dev/console
When finally you want to close the connection, you resume and
terminate kermit. The last line of the script kills the local TERM and
returns the system in its initial state.
( Note of the author: instead of doing '!killall -KILL term', I think
it should be possible just to do '!tshutdown'. This should also work?)
As I said, there are zillions of ways to do so; these are just meant
as examples to get you started. Other examples can be found in the
packages autoterm and JoelTermStuff.
10. Porting software for use with TERM
In principle, all programs that can be used over a network can also be
used in combination with TERM. Some of them you can get as binaries
with TERM support already built in. These include telnet, (nc)ftp,
Mosaic and many others. Most of these programs are compiled for TERM
1.17 or earlier. They should, however, still work with the newer
versions of TERM.
Another way to make programs TERM aware is to port them yourself. This
process will be described in the next subsection.
The last way to make your programs TERM-aware is to termify them.
10.1. Port and compile the sources
Porting software to TERM can be done using a fairly simple porting
procedure:
If installed in '/usr/local' by root:
1. Add to the compile flags -include /usr/local/include/termnet.h
2. and add to the library list -ltermnet
If installed in your home directory:
1. Add to the compile flags -include $HOME/term/termnet.h
2. and add to the library list -L$HOME/term -ltermnet
Now compile the software as described in the INSTALL or README
document that came with the software. That should do!
At this point the commands should work both with and without TERM.
telnet localhost
does not use TERM to connect, but
telnet bohr.physics.purdue.edu
will use TERM only if you do not have some other type of network
connection.
Some commands like rlogin can only be executed by root and the owner
of the TERM connection (privileged persons).
Some TERM commands will be TERM transparent and only use TERM when
there is not another option. Some common examples are telnet and ftp.
Others require an external flag to tell them it is all right to use
TERM. These programs include xarchie, fsp and ytalk.
You can either flag these programs to use TERM by setting the
environmental variable TERMMODE as specified in README.security, or
running make installnet. Eventually, the 'termnet' file created will
contain special networking instructions, but for now only its
existence is checked.
If you add an ethernet connection, you can then simply remove the
'termnet' file and continue to use the same binaries!
NOTE: Programs that were ported back in the days of client.a, can
still be recompiled for use with newer versions of TERM simply by
changing the client.a reference to libtermnet.a.
10.2. Termify
This package will convert dynamically linked binaries for TERM use.
Before you can use termify you have to make sure that you have TERM
version 2.2i (is this version 2.2.8?) or later and libc.so.4.5.26 or
later. Then you have to create the file 'libt.so.4' in the directory
'/lib' (see the README file in the package).
Problem at this moment is that you have to remake the file 'libt.so.4'
every time you upgrade TERM versions.
After you have created the library you can let termify 'crunch' the
program you want to make TERM-aware, by using the command:
termify <command name>
When you do not like the result you can 'un'termify the program you
have just termified using the command:
termify -u <command name>
Last, the package also contains a script for completely termifying
'smail'; so no special transport definitions are necessary. The only
thing you possibly want to change is the 'From: ' address.
11. Term clients
11.1. Term clients available on ftp sites.
Below a list of application running with TERM is given. I am not
stating that this list is complete; so any completion is welcome. As
far as possible I will present the site and directory where the
application can be found (all to my knowledge). When I state
sunsite.unc.edu as the place to find the application I mean that you
can find it in one of the following two directories:
1. /pub/Linux/apps/comm/term/apps
2. /pub/Linux/apps/comm/term/extra
Here we go :-)
TERM package:
tupload
tdownload (versions 2.1.0 and higher)
trsh
tmon
tredir
tudpredir (versions 2.0.0 and higher)
txconn
trdate(d)
tshutdown
libtermnet
File transfer:
ftpd sunsite.unc.edu
termncftp sunsite.unc.edu
ncftp185 sunsite.unc.edu:/pub/Linux/system/Network/file-transfer
fsp sunsite.unc.edu:/pub/Linux/system/Network/file-transfer
Information systems:
lynx
Mosaic sunsite.unc.edu:/pub/Linux/system/Network/info-systems/Mosaic
chimera
netscape sunsite.unc.edu:/pub/Linux/system/Network/info-systems
httpd
xgopher
gopher sunsite.unc.edu
Remote login:
termtelnet sunsite.unc.edu
rlogin physics.purdue.edu:/pub/bcr/term/extra
rsh physics.purdue.edu:/pub/bcr/term/extra
Netnews:
tin 1.3 sunsite.unc.edu:/pub/Linux/system/Mail/news
news2 sunsite.unc.edu
Mail:
slurp sunsite.unc.edu
smail sunsite.unc.edu
term.mailerd+smail sunsite.unc.edu
BCRMailHandlerXXX physics.purdue.edu:/pub/bcr/term
Automating scripts:
JoelTermStuff sunsite.unc.edu
autoterm sunsite.unc.edu
fet sunsite.unc.edu
Other programs:
inetd sunsite.unc.edu
rdate sunsite.unc.edu
xgospel sunsite.unc.edu:/pub/Linux/games/x11/networked
termify physics.purdue.edu:/pub/bcr/term/extra
xboard sunsite.unc.edu
ircII sunsite.unc.edu:/pub/Linux/system/Network/chat
whois
xwebster sunsite.unc.edu
sxpc ftp.x.org:/R5contrib
xztalk sunsite.unc.edu:/pub/Linux/apps/sound/talk
11.2. The termnet package
The package termnet-2.0.4-Linux-bin.tar.gz
(sunsite.unc.edu:/pub/Linux/apps/comm/term) contains a couple of pre-
compiled TERM clients and a couple of scripts, manual pages and
libtermnet.so.2.00.04. The clients are compiled using this version of
libtermnet.so. The package contains the following clients:
fet perl sperl4.036 tmon tshutdown xgopher
finger perl4.036 suidperl trdate tudpredir ytalk
ftp rcp taintperl trdated tupload
fwhois rlogin telnet tredir txconn
ncftp rsh term trsh xarchie
WARNING: The package also contains the complete set of compiled
clients of TERM 2.0.4 including TERM itself. Do not install this
package before you are sure about what you want. You will destroy
other versions of TERM and its clients when you start moving
executables around.
11.3. Asked for but not yet supported
1. DOOM: The problem with this game seems to be the fact that it uses
port 5029 both as client and as server.
2. NFS: The NFS server is only supposed to accept requests if the
socket requesting the connection is bound to a port below 1024.
This seems to be troublesome. However, some NFS servers have an
'insecure' option. In this case NFS might work eventually, if RPC
support is added to Term.
12. Term and Security
In this section I will point to some security aspects of TERM. The
problems will be explained and a way to improve security will be
given.
12.1. trsh
Trsh is insecure when it is used to access the local Linux box from
the remote system. The problem with TERM and its clients is that
beside the owner of the TERM connection also 'root' can execute TERM-
aware programs over the connection.
This also means that 'root' on the remote system can execute trsh and
thus can enter the login which owns the TERM connection quite easy. If
this owner on the local box is 'root' then you will be in hell.
The solution to this problem is easy: you just have to put the
following line in the termrc� file on the local box:
denyrsh on
With this set in the 'termrc' file, nobody can use trsh on the remote
site anymore to access your machine. When you and others want to
access your local Linux box over the TERM connection this can still be
done using telnet and redirected ports.
12.2. txconn and xauth
Txconn is not terribly secure; anyone can connect to your local server
via TERM and perform all sorts of mischief. I you are worried about
this sort of thing, it might be a good idea to consider using xauth to
authorize your connections. See the next section for an example of
using xauth for securing your connections.
12.3. sxpc, xhost and xauth
Sxpc in combination with 'xhost +' is very dangerous when you are not
using xauth.
Using xauth is very important to maintaining security when using sxpc.
If you do not use xauth when using sxpc all the dangers of running
with 'xhost +' apply. These dangers include but are not limited to:
� Someone watching what is displayed on your screen
� Someone watching what you type
� Someone typing in one of your windows (for example: a command to
delete all your files :-(
Xauth is available in X releases R4 and later. Here I will describe
how to set up basic usage of xauth. This configuration is vulnerable
to network snooping, but if you can live with that it should be fine.
NOTE: when using xauth your $DISPLAY variable must NOT be set to
localhost (or localhost:whatever). If your $DISPLAY variable does use
localhost the clients will be unable to find the appropriate
authorization information. The workaround is to use the real hostname
of the machine. If you follow the compilation instructions in the
README, and compile without -DNOGETHOSTNAME then everything should
work.
The machine where you will be running clients will be called C, the
machine where you wish to display them will be called D.
First choose a 'key', up to 16 pairs of hexadecimal digits (so an even
number of characters from the ranges 0-9 and a-f). You will need to
supply this key in place of <key> in the example below.
On C:
% xauth
xauth: creating new authority file $HOME/.Xauthority
Using authority file $HOME/.Xauthority
xauth> add Chostname:8 MIT-MAGIC-COOKIE-1 <key>
xauth> exit
On D:
% xauth
xauth: creating new authority file $HOME/.Xauthority
Using authority file $HOME/.Xauthority
xauth> add Dhostname/unix:0 MIT-MAGIC-COOKIE-1 <key>
xauth> add Dhostname:0 MIT-MAGIC-COOKIE-1 <key>
xauth> exit
When starting the X server on D you should give the flag -auth
$HOME/.Xauthority. You may need to edit or create a
'$HOME/.xserverrc' to control how the X server is started. For
example:
#!/bin/sh
exec X -auth $HOME/.Xauthority $*
Make sure that your '.Xauthority' file is readable only by you on both
C and D.
13. Things to remember
In this section I try to present you with a list of useful ftp
addresses, URL's etc. where you can find software and information
about TERM.
Ftp:
sunsite.unc.edu:/pub/Linux/apps/comm/term/<whole-directory-tree>
sunsite.unc.edu:/pub/Linux/docs/HOWTO/<whole-directory-tree>
physics.purdue.edu:/pub/bcr/term/<whole-directory-tree>
URL:
http://sunsite.unc.edu/mdw/HOWTO/Term-HOWTO.html
http://www.bart.nl/~patrickr/term-howto/Term-HOWTO.html (always the newest version)
http://physics.purdue.edu/~bcr/homepage.html
Netnews:
comp.os.linux.announce announce of new TERM versions and Term-HOWTO
comp.os.linux.help ask your questions about TERM here
comp.os.linux.misc or here
comp.protocols.misc answers to TERM questions are also posted here.
Related documents:
Using Term to Pierce an Internet Firewall HOWTO by Barak Pearlmutter,
[email protected]
Firewall HOWTO by David Rudder,
[email protected]
Serial HOWTO by Greg Hankins,
[email protected]
Net-2/Net-3 HOWTO by Terry Dawson,
[email protected]
When you start asking questions on netnews please make sure that you
give people in the groups as much information as they need to solve
your problem (TERM version number, way you set up your connection
etc.). At this moment many TERM versions are in use and all have their
specific and common problems. Therefore, when you want a useful
answer, at least state the version of TERM you are using. Otherwise,
in some cases only wild guesses are possible to help you solve your
problems.
14. Reliability of TERM versions
Many versions of TERM are around now. The maintainer of TERM, Bill
Riemers, has made a list of TERM versions stating what versions are
reliable and what versions you had better avoid. This list is the
following:
term110 --> cannot really say
term111 --> cannot really say
term112 --> cannot really say
term113 --> cannot really say
term114 --> fairly stable BETA version
term115 --> unstable BETA version
term116 --> unstable BETA version
term117 --> unstable BETA version
term118 --> semi-stable BETA version
term119 --> stable GAMMA version
term-2.0.X --> semi-stable BETA versions
term-2.1.X --> more stable BETA versions
term-2.2.X --> new BETA versions
term-2.3.X -->
15. Term speed table
Thanks to Bill McCarthy we now have a table with TERM speed
information for different modems, TERM versions and connection
conditions. Its purpose is to give new and experienced users some idea
what other people are using and the results they are getting.
LINUX TERM CHART 8/14/94
|___modem speed/make___|___line speed__|__avg cps__|__high__|__term ver_|
| 1) USR SP 14.4 | 9600 | 950 | 963 | 1.17 |
| 2) USR SP 14.4 | 14400 | 1376 | n/a | 1.18p06 |
| 3) Zoom 2400 | 2400 | 220 | 230 | 1.19 |
| 4) Boca V.32bis 14 | 57600 | 1400 | n/a | 1.01/09? |
| 5) Viva 14.4 | 14400 | 1300 | n/a | 1.16 |
| 6) USR SP 14.4 | 14400+ | 1550 | 1680 | 1.19 |
| 7) Intel 14.4 Fax | 14400 | 1400 | 1650 | 2.0.4 |
| 8) cable tv hookup | 57600 | 1500 | 1800 | 1.18p06 |
| 9) Twincom 144/DFi | 57600 | 1500 | 4000? | 2.0.4 |
| 10) USR SP 14.4 | 14400 | 1200 | 1500 | 1.08 |
| 11) cable tv hookup | 19200 | 1300 | 1800 | 1.19 |
|-----------------------------------------------------------------------|
+Command flags/termrc settings:
1) default escapes 2) window 5 3) baudrate 2400 4) n/a
baudrate 9600 timeout 200 window 3
window 10 noise on
timeout 150
5) compress off 6) baudrate 19200 7) ignore 19+17 8) compress off
window 10 compress on window 4 escape 0, 13,
timeout 150 timeout 90 16-19, 255
baudrate 38400 baudrate 0
shift 224
flowcrtl 500
window 10
timeout 70
retrain on
breakout 24
9) compress off 10) compress off 11) baudrate 19200
baudrate 57600 baudrate 38400 compress on
window 10 escape 17, 19 shift 224
timeout 200 remote escape 0, 13 16-17
noise on 19, 255
share on window 10
remote timeout 40
Escaping characters at one end also implies ignoring them on the other end.
16. Hints and Tricks found on the net
In the Linux related newsgroups many questions about TERM are coming
back every couple of weeks, together with the answers to these
questions. To reduce traffic to the newsgroup, in this section I shall
try to make a composition of these questions and the answers to them.
Some of the answers have been checked by me as I also had related
problems. Others, I have just taken from the newsgroups without
testing them.
� Many people, especially those who are using Ultrix, seem to have
trouble with vi presenting less than 24 lines on a window with 24
lines. There are three ways to get rid of this problem:
1. Log in into the remote system using:
trsh -s telnet <hostname>
2. Put 'resize; clear' in your '.login' file
3. The best solutions seems to be to enter the following remote:
stty 38400
� Many people seem to have problems with crashing TERM connections,
whatever may be the reason of the crashes. So before starting
applications people want to know whether their TERM connection is
still alive or not. This can be checked using the following small
shell script examples:
When you are using tcsh:
if ( { trsh -s true } ) then
...
endif
When you are using bash:
if trsh -s true; then
...
fi
� The WWW browser Netscape is causing people problems to get it to
work with TERM. The good news is that it will work under TERM. Here
is how:
1. Termify netscape
2. Fire up termnetscape
under Options | Preferences | Mail/Proxys
leave _all_ of the proxy boxes blank
set the SOCKS box to 'remotehost' & 80
3. Ignore the error you get when you exit the Options menu.
4. If termnetscape fails to work right:
under Options | Preferences | Mail/Proxys
leave _all_ of the proxy boxes blank
set the SOCKS box to 'none' & 80
5. Ignore the error you get when you exit the Options menu.
Scott Blachowicz mailed me stating that it is even easier to get
Netscape or any other browser to work with TERM if you have a proxy
server (e.g. CERN's httpd) installed for use on the remote side of
your TERM link. On the local side, you can then do this:
1. tredir localhost:8080 remotehost:80
where 'remotehost' is the hostname of your proxy server system.
2. Run your particular browser, then in the preferences or options or
whatever it is called, point your proxies at 'localhost' port
8080.
Some browsers might like environment variables like
export http_proxy=
http://localhost:8080/
export ftp_proxy=
http://localhost:8080/
17. Other Things
Some things that might be included:
� Extension of troubleshooting
� Extension of security issues
� Termwrap
� Suggestions
Anyway, if you have suggestions, criticism, suggestions, or anything
else to say about this document, please fire away. At the moment I,
Patrick Reijnen, have taken over the authorship of the TERM-HOWTO. I
can (currently) be reached at
[email protected].
18. Acknowledgements
A lot of people have to be thanked. First and foremost Michael
O'Reilly and all the developers of TERM, who have provided us with
such a great tool. I would also like to thank everyone who gave
feedback and contributed to this HOWTO. They include Bill Reynolds,
the former author of this HOWTO, Ronald Florence, Tom Payerle, Bill C.
Riemers, Hugh Secker-Walker, Matt Welsh, Bill McCarthy, Sergio, Weyman
Martin and everybody I forgot to mention.
