SLIRP(1) Version 1.0b SLIRP(1)
9 Jan 1996
NAME
slirp - TCP/IP emulator
SYNOPSIS
slirp [options|commands]
slirp help
slirp "help cmd"
DESCRIPTION
Slirp is a TCP/IP emulator which turns an ordinary shell account into
a (C)SLIP/PPP account. This allows shell users to use all the funky
Internet applications like Netscape, Mosaic, CUSeeMe, etc.
Slirp is copyright (c) 1995 Danny Gasparovski. All rights reserved.
See the section COPYRIGHT for details.
This manpage is organized as follows. First, basic usage is described
very briefly. This is followed by details of configuration files,
commands, and command-line options. Several sections discussing
technical issues (special addresses, port redirection, baudrate
setting) are next, followed by answers to frequently-asked questions
and common problems. Contact information, acknowledgements and the
copyright notice are at the end.
Please read this manpage thoroughly before reporting problems!
USAGE
To run Slirp, simply type:
slirp
(or whatever the full path to Slirp is). That's it. Now you activate
your SLIP/PPP software, and start your applications.
All you have to remember is this: Once you run Slirp, your shell
account now looks exactly like a SLIP/PPP account (with some
limitations of course). Any documentation that you have telling you
how to connect to a SLIP/PPP account is completely valid for Slirp as
well.
To quit Slirp you simply kill your SLIP/PPP software and type five 0's
(zeroes), with a 1 second gap between each zero. Slirp will then exit
and you will be back at your shell prompt.
You can also "disconnect" Slirp by typing five 1's (one's), with a 1
second gap between each. This will disconnect Slirp from your shell's
terminal and put Slirp in the background. Later, you can type
slirp -l 0
to "reconnect" Slirp again.
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Quick note for PDA users: If you set SLIRP_TTY to the tty connected
to your PDA (Palm, POSE emulator, etc.), Slirp will use that tty for
communication. You can use PPP without full masquerading, although
you will be subject to the standard Slirp constraints. You may need
to experiment to find the correct baud rate. Start with 19200 for
Palms. If Slirp was not compiled with DO_CFSETSPEED, you'll need to
set the speed on the tty manually. Use an appropriate variant of
"stty 19200 < /dev/pilot" after starting slirp.
CONFIGURING SLIRP
Slirp can be configured in 3 different ways: the command line, the
configuration files, and "on-the-fly" configuration by telnet-ing to
10.0.2.0 and entering the commands there (see "SPECIAL ADDRESSES,"
below).
The configuration file is located in your home directory (~) and is
called ".slirprc", hence the path to your configuration file is
"~/.slirprc".
Options which can appear in a configuration file can also be given on
the command line. E.g., If your .slirprc file looks like the
following:
redir 5022 21
redir X
you can achieve the same thing by running Slirp as:
slirp "redir 5022 21" "redir X"
(Notice the quotes, they ARE significant). The reverse is also true.
E.g., if you run slirp as:
slirp -P -b 14400
you can create your .slirprc file too look like the following:
-P
-b 14400
(Notice that only ONE command per line is allowed in configuration
files). The 2 types of options can also be mixed. For example:
In .slirprc:
-P
-b 14400
redir 5022 21
Command line:
slirp -P -b 14400 "redir 5022 21"
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Note that on the command line, any command/option that does not begin
with a '-' or '+', and has spaces in it, MUST be enclosed in quotes.
E.g., The following are all legal:
slirp -P "redir udp 5022 25" -vj -b 14400
slirp "ppp" "baudrate 14400"
slirp ppp "baudrate 14400"
(Notice that even though "ppp" does not begin with a '-' or '+', it
does not need to be enclosed in quotes because it has no spaces in it)
The following are NOT legal:
slirp baudrate 14400
slirp "-b 14400"
(Because "-b" starts with a '-' you must NOT enclose it in quotes.)
Easy, eh?
Note: Whenever Slirp expects an IP address as an argument (E.g., in
the command "redir") and the IP address argument is not given, then
the default used is different depending on where the command appeared;
if it was in ~/.slirprc then the default is 10.0.2.15; if it was in a
telnet 10.0.2.0, then the IP address used is the IP address from where
the telnet 10.0.2.0 connection was made. For example, if you have a
LAN at home and telnet to 10.0.2.0 from one of the hosts and issue a
"redir" command, Slirp will use the IP address of the host from where
you made the telnet 10.0.2.0 connection. Also, if you use an IP
address on your PC other than 10.0.2.15, you should include it as an
argument whenever Slirp expects it, for example with the redir
command:
redir 5555 your.ip.address:5555
A few notes on configuration:
* You should have "ppp" or "-P" before any PPP options (because when
Slirp parses -P or ppp, it will initialize all related fields,
hence clearing anything that was parsed before it).
* Upon startup, the configuration is done in this order:
1) ~/.slirprc-N (if using Load-balancing or Link-resumption)
2) ~/.slirprc
3) Command-line options
This is important because, for example, if you have "initiate-
options" (a PPP option) in ~/.slirprc-0, and you run slirp with
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-P, "initiate-options" will not be valid, because -P will clear
the fact that you want options initiated by Slirp (remember, -P
should always come before any PPP options).
COMMANDS AND OPTIONS
Slirp includes an "online-help" facility. To get a list of commands
accepted by Slirp give it the command "help". I.e, you can either run
Slirp from your shell prompt as:
slirp "help"
or once Slirp is running, telnet to 10.0.2.0 and type:
help
To get a brief description of each command simply type "help COMMAND".
E.g.:
slirp "help baudrate"
from the command line, or
help baudrate
in telnet to 10.0.2.0.
In the following descriptions, items within square brackets are
optional. "Usable" refers to where it can be used, ie: "command-
line/config-file", "telnet", or "anywhere" (which means it can appear
in either command-line/config-file or be given via telnet).
"Command-line" gives the command-line equivalent, where applicable.
redir X [start N] [ADDR][:DISPLAY[.SCREEN]]
Redirect a port for use with the X Window System.
Usable: anywhere
Command-line: -X
Options:
start N
Tell slirp to start looking for free ports starting from N.
eg: if N = 2, slirp will try to grab port 6002 then 6003
etc. this is useful for sites which sometimes run their own
X server and you don't want to nab their port 6000, which
they would naturally expect.
ADDR
Our home ip address, or the address where the X server is
(if you have a LAN at home to connect more than one machine
to the net) (default 10.0.2.15 when in ~/.slirprc, the
source IP address when in command-line).
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DISPLAY
Which display to redirect to (default :0).
SCREEN
Which screen to redirect to (default .0).
Example: redir X 10.0.2.15:0.0
Note: This will print the command needed to enter into each shell
from where you launch your X apps.
See also: show X.
show X
Show the command that needs to be given to your shell for any X
port that has been redirected (in case you forget).
Usable: telnet
Example: show X
Note: This is useful if you forget the command to give to your
shell for X redirection.
See also: redir X, log start.
redir [once|time] [udp|tcp] PORT [to] [ADDRESS:]LPORT
Redirect host port to local port using a selected protocol.
Usable: anywhere
Options:
once Only allow one redirection [TCP only]
time Allow redirection to time out [UDP only]
udp Redirect a UDP port
tcp Redirect a TCP port [default]
PORT Port to use on host system
ADDRESS Address of your home machine [default 10.0.2.15]
LPORT Port to redirect host port to on local system
Example: redir tcp 5021 to 21
Allow users to ftp to your local machine using your host's port
21. (ftp your.hosts.name 5021).
Note: if this command is in your .slirprc file and no address is
specified, it will assume that your local IP address is 10.0.2.15.
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If you enter the command from the slirp control telnet IP it will
use the IP address you are accessing with.
baudrate N
Controls the allocation of time to communications across your
serial link. Higher values generally use more of the available
bandwidth to your modem. This is _only_ an internal control value
and does _not_ change the physical settings for the host port or
modem.
Usable: anywhere
Command-line: -b
Example: baudrate 14400
Note: higher numbers generally allow better transfer rates for ftp
sessions, but interactive sessions could become less responsive.
the optimum value is *JUST* when ftp sessions reach maximum
throughput, but this can be hard to find (especially on
compressing modems) so you should choose the maximum throughput
you would expect from your modem.
special|control|host addr ADDRESS
Set ip address aliases and others for slirp.
Usable: anywhere
Options:
special address
Set the network ip alias for slirp
control address
Only allow access to slirp control address from ADDRESS.
host address
Tell slirp the IP address of the host it's running on. Use
this only if slirp can't properly find the host's IP
address.
Example: special address 10.0.3.0
Note: The ADDRESS for special must end in 0 (zero) and other
addresses are classed from this. The default special address is
10.0.2.0 giving the following defined IP's:
10.0.2.0 slirp control telnet IP
10.0.2.1 slirp exec IP
10.0.2.2 slirp host alias
10.0.2.x add [pty]exec optional address
add [pty]exec PROGRAM:[ADDRESS:]PORT
Set program to execute on host when local machine attempts to
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connect to ADDRESS at port PORT.
Usable: anywhere
Options:
exec Establish binary connection to program in the style of
inetd.
ptyexec Establish telnet connection to program using telnetd
helper application under a pseudo-terminal.
PROGRAM Program to exec
ADDRESS Optional address
PORT Port
Example: add ptyexec csh:55
A telnet connection to the slirp exec IP (default 10.0.2.1) will
start and connect you directly to the csh program on the host.
(telnet 10.0.2.1 55).
Example: add exec nntpd:10.0.2.3:119
A program that attempts to open port 119 at address 10.0.2.3 will
be connected to the nntpd program.
Note: The use of the ptyexec form requires the slirp.telnetd
helper application be available on your path. Also note that
ADDRESS must be of the form SPECIAL_ADDRESS.xx (10.0.2.xx by
default).
[no]compress
Force startup mode for slirp to SLIP or CSLIP. This overrides the
default automatic mode determination.
Example: nocompress
Start in SLIP mode.
Example: compress
Start in CSLIP mode.
Note: The default method of operation generally performs well. You
should only have to use this command if you find that your host
and local system are failing synchronize the connection type.
mtu N
Controls the size of the IP packets sent across the serial IP
link. Valid values are <= 1500.
Example: mtu 1500 Set the mtu to its largest allowable size.
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Note: Larger values generally improve the performance of graphics
web browsers and ftp transfers across the serial link, at the
expense of interactive performance. The default value of 552 seems
to be a reasonable compromise for connections at 14400 baud.
shell PROGRAM
Set program to execute on EXEC IP default telnet port (23).
This is the same as
add ptyexec PROGRAM:23
Note: By default slirp connects /bin/sh to the exec IP telnet
port.
help [COMMAND]
Show a brief list of available commands, or more information on
the named command.
remove [pty]exec PROGRAM:[ADDRESS/]PORT
Reverse the effect of "add [pty]exec". see "add [pty]exec" for
the options etc.
Note: you must enter the options exactly as you entered it in add
[pty]exec.
**This description is incomplete.**
echo [on|off]
Turn echo on or off, depending on how your client behaves. "echo"
by itself will show whether echo is currently on or off.
kill N
Kill the session which has a Socket no. of N. to find the Socket
no. of a particular session, use the "stats socket" commands.
See "stats" below.
Note: It is recommended you use "close N" instead, as this merely
wipes out the session, whereas "close N" closes it properly, as a
good little tcpip-emulator should :)
"kill -1" shouldn't be used, it will kill the first session it
finds with -1, which usually is the command-line connection.
close N
Close the session which has a Socket no. of N. same as "kill N",
but closes it session gracefully. See "kill N".
stats [ip|socket|tcp|vj|udp|mbuf|tty|alltty|others?]
Show statistics on the given argument.
Options:
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ip Show ip statistics.
socket Show statistics on the currently active sockets. Use this
to find out which sessions to close/kill as it will also
show the FD of the session.
tcp Show tcp statistics (packets sent, received, etc).
udp Same as tcp but for udp.
mbuf Show how many mbufs were allocated, are in use, etc. If
the modem is idle, and there are more than 1 mbufs on the
used list, it suggests an mbuf leak.
[pty]exec PROGRAM
This will execute PROGRAM, and the current command-line session
will cease to exist, taken over by the PROGRAM. ie: when the
program exits, you will not get the command-line back, the session
will (should) close.
socket [PORT,PASSWORD]
Create a Unix-domain socket and listen() for more interfaces to
connect. This is also needed for restarting. Give the arguments
PORT,PASSWORD if you wish to use Internet-domain sockets instead
of UNIX-domain sockets.
log start
Log all the startup output to the file .slirp_start.
add emu SERVICE[:TYPE_OF_SERVICE] [lport:]fport
Tell slirp to emulate SERVICE when on port lport/fport.
Options:
SERVICE
Can be: ftp, ksh, irc, none.
TYPE_OF_SERVICE
Can be: throughput, lowdelay.
LPORT
Can be given if that service needs emulation for, say,
servers.
Example: add emu ftp 8021
If you wish to ftp to somewhere on port 8021.
Example: add emu ftp 8021:0
If your home ftp server is on port 8021. NOTE: this does NOT mean
if you redirect port 8021 for your ftp daemon, it refers the the
port AT HOME at which ftpd is listening to.
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Example: add emu none:lowdelay 8000
If you telnet somewhere on port 8000, and you wish those packets
to go on the fastq (ie: so they have a higher priority than, say,
ftp packets). This tells slirp that any packets destined for port
8000 will not have any emulation, but it will be set
IPTOS_LOWDELAY.
dns DNS_IP
Give this to slirp if you want to use 10.0.2.3 as an alias for
DNS, AND slirp guesses wrong for the DNS on startup.
TECHNICAL TOPICS
Special Addresses
All addresses of the form 10.0.2.xxx are special to Slirp (this can be
changed with the "special addr" command). The following is a
description of what each of the addresses mean:
10.0.2.0
This is the Slirp "on-line" configuration address. When you
telnet to 10.0.2.0 you can close connections, configure Slirp,
redirect ports, etc. all while Slirp is running. Please read
the section "CONFIGURING SLIRP" for details on how to use this.
10.0.2.1
This is the address used by Slirp to execute programs. For
example, if you give Slirp the command "add exec /bin/ls:23",
when a connection is made to 10.0.2.1 on port 23, Slirp will
execute /bin/ls and redirect the output to that connection.
E.g., with "add exec /bin/ls:23", if you telnet to 10.0.2.1
(telnet uses port 23) you will get a list of files in the
directory Slirp was started. Another example could be "add exec
/path/to/nntpd:119". Now you can tell your News reader to use
10.0.2.1 as the News host and it will actually connect to the
running program "nntpd".
10.0.2.2
This is an alias for the remote host. When you connect to
10.0.2.2 you will actually connect to the host Slirp is running
on. This is useful if your shell account can be on different
hosts, 10.0.2.2 will always mean the host Slirp is running on.
10.0.2.3
This is an alias for your DNS. Slirp will try to figure out your
DNS address and all data sent to 10.0.2.3 will be redirected to
your DNS address, so you can tell your TCP/IP software to use
10.0.2.3 as your DNS. This can also be useful if your run Slirp
from multiple hosts; you don't need to change your DNS for each
host.
10.0.2.15
This is the address recommended by Slirp to be used on your PC.
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However this is merely a suggestion, Slirp does not care what
address you use.
Port Redirection
Port redirection is an important concept in TCP/IP emulators because
it allows other people to connect to your PC, as well as allowing some
programs to work which normally would not work.
How do I Redirect a Port?
First you need to realize that under Slirp, nobody on the Internet can
address your PC directly, since you do NOT have an IP address that
anybody else can see. The ONLY way they can contact you is through the
remote host (where Slirp is running).
What has this got to do with Port redirection? Lots. For other
people on the Internet to be able to connect to your PC, Slirp needs
to listen for connections on a specific port on the remote host, then
"redirect" this connection and have it connect back to your PC.
For example, say you are running an FTP server on your PC and you want
others to be able to connect to it, get files, upload files, etc.
What you need to do is pick a port number, any port number above 1024
(for security reasons), and tell Slirp that any connections on that
port are really connections to your FTP server. You do this with the
"redir" command.
For this example, say you choose 5555 as the port to redirect (this
can be ANY number, provided nobody else is using it). You simply give
Slirp the command:
redir 5555 21
The second argument, 21, is the port that is used by FTP. You could
have also used the command:
redir 5555 ftp
and Slirp will figure out that "ftp" means 21. This command is
basically telling Slirp "any connections to this host (where Slirp is
running) on port 5555 are really connections to the home PC on port 21
(the port used by the FTP server)".
Now you simply tell others to connect to the Remote Host (where Slirp
is running), which IS visible on the Internet, on port 5555 and they
will be connected to your FTP server.
This same technique is used when a program uses a specific port for
communication, for example Kali, an IPX emulator over TCP/IP allowing
users to run IPX games over the Internet. Kali uses UDP port 2213 for
communication so for others to be able to send a packet to your PC on
UDP port 2213 you need to do the following:
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redir udp 2213 2213
All packets now destined for the Remote Host on UDP port 2213 will be
sent to your PC on port 2213.
Common Port Redirections
Here is a list of programs which need a port redirection to work.
YOUR_PC_ADDRESS refers to the IP address you assigned to your PC. If
it is not supplied, 10.0.2.15 is assumed.
Kali
redir udp 2213 YOUR_PC_ADDRESS:2213
(Note: you MUST also set your PC's IP address to the same IP
address as the Remote Host (where Slirp is running))
IPhone
redir udp 22555 YOUR_PC_ADDRESS:22555
StreamWorks
redir udp 8000 YOUR_PC_ADDRESS:8000
(the 8000 is configurable)
PowWow
redir tcp 13223 YOUR_PC_ADDRESS:13223
WebPhone
redir tcp 21845 YOUR_PC_ADDRESS:21845
redir udp 21845 YOUR_PC_ADDRESS:21845
(Note: WebPhone uses BOTH tcp and udp port 21845. In addition, you
probably need to set your PC's address to the same IP address as
the RemoteHost in order to get full functionality)
Please let me know of other programs which require redirection like
the above. See "GETTING HELP" for details on how to contact me.
Setting The baudrate Option
Slirp's "baudrate" option has caused some confusion. This section
will explain exactly what it's for and how to use it.
When sending data over the modem to your PC, Slirp needs to know how
much data it can send over without "saturating" the link. If Slirp
was to send as much data as it could, the Operating System would
buffer a LOT of it - 20k is not uncommon. This could severely "lag"
any telnet connections if you happen to be FTP-ing a file at the same
time. This is because when you type a character, you will not see
that character on the screen until the the other end sends you the
"echo", so if there is 20k worth of data buffered you will need to
wait until 20k of data is received before you see that character on
your screen.
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To counter this, Slirp uses the "baudrate" option to limit the amount
of data it sends over the link to prevent the Operating System from
buffering too much of it. So if you give Slirp a "baudrate" of 14400,
Slirp will send data at a rate of 14400 Baud modem (with no
compression).
In general, the baud rate at which the connection was made should be
the "baudrate" you give to Slirp. So, for example, if you connected
at 14400 Baud, you should give Slirp the option "baudrate 14400".
However, since most modems today do compression (v.42bis), it is very
difficult for Slirp know how much data to send to keep the link
"full", yet prevent too much buffering by the Operating system.
Therefore you should choose a "baudrate" appropriate to your needs: if
you use telnet a lot while downloading compressed files, you should
set your "baudrate" to the same as the CONNECT speed of your modem.
Downloading compressed files should not suffer, and telnet sessions
will be far more responsive. However, sending text over the modem
will not be as fast, because your modem will compress the data and
send it faster than Slirp expects. Giving a "baudrate" the same as
the CONNECT speed will effectively turn off modem compression.
If you do not use telnet very much, you should set your "baudrate" to
the maximum theoretical speed your modem can do. For example, if you
connect at 14400 and use v.42bis compression, which can compress up to
4x, you should set your "baudrate" to 14400*4 = 57600. This will
ensure any compressible data will get compressed, and a maximum
throughput will be attained, at the expense of telnet sessions which
will be almost unusable if you happen to be downloading files at the
same time.
Note however that you can change the "baudrate" setting at any time.
Simply telnet to 10.0.2.0 and enter "baudrate XXX" and Slirp will
change the rate at which data is sent. This can be useful for example
if you're downloading a lot of compressed files, but in the middle of
the download you want to read mail. Simply change the "baudrate" to
the CONNECT speed, and when you're finished, change it back to the
maximum theoretical speed.
Also, keep in mind that the "baudrate" is also used for other
calculations. For example, if there are many connections, Slirp will
try to be fair and send one packet per connection in a round-robin
fashion. This makes all connections "smooth" instead of sending a
bunch of packets for one connection, then a bunch of packets for
another connection, etc. But if the "baudrate" is too high, the is
exactly what will happen. Packet priority selection also uses the
"baudrate"; I.e., if there are packets queued ready for sending from
both an FTP connection and a telnet connection, the telnet packets
will be sent first. But again, this will only work if the "baudrate"
reflects the amount of data Slirp can send, and generally won't work
if you set it to the maximum theoretical connection speed.
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So here are my tips:
* If you download a lot of compressed files and occasionally use
telnet, or other "interactive" programs, set your "baudrate" to
your CONNECT speed (because already compressed files won't
compress any more with the modem compression, so you're unlikely
to get faster download's as a result of modem compression);
* If you mainly use telnet, or other "interactive" programs, and you
occasionally download some compressed files, set your "baudrate"
to the maximum theoretical speed (because telnet sessions are
usually text, which compresses very well, hence screen updates
will be faster. Only when downloading compressed files will you
experience severe lag);
* If you mainly browse the Web (E.g., using Netscape, etc.), then
you should set your "baudrate" to the theoretical maximum speed
(because there's lots of text in Web documents which is very
compressible, and there's no telnet sessions so lag will not be a
problem);
I personally have by baudrate set at 14400, the speed at which my
modem connects, even though the modems do v.42bis compression.
Compressed file downloads are just as fast, and telnet sessions during
FTP downloads are surprisingly responsive. Try it yourself, there's a
world of difference.
PROBLEMS, QUESTIONS, AND ANSWERS
Which programs do not work over Slirp?
Any programs that bind()'s a port, then tell the other end of the
connection where they should connect() to this bound port.
For example, when you "get" a file during an FTP session, the FTP
client bind()'s a socket, has a look at which port the socket is bound
to, then tells the FTP server the address and port of this socket
(with the PORT command). The FTP server then connect()'s to this
address/socket pair.
Now, since your machine isn't really on the Internet, this connect()
request will not arrive to your host, so it will not work.
Slirp emulates this by bind()ing it's own port on the server that *is*
on the Internet, and tells the FTP server about *that* address/socket
pair. When the server connect()'s to it, Slirp will then connect back
to your machine.
At present, the following programs are emulated:
rlogin
ftp
ksh
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irc (for /dcc)
RealAudio
talk/ytalk/ntalk
CUSeeMe
Troubleshooting
Symptom:
The connection will "freeze". E.g., while downloading a picture
on WWW it will stop halfway and no connections will continue.
Diagnosis:
You probably don't have an 8bit clean link.
Cure:
You should try and find out from your sysadmin which characters
need to be "escaped", then tell Slirp about them using the
"asyncmap" and "escape" commands. Note that you need to use PPP
for this to work. (One way to test for 8bit cleanliness is to
download a BINARY file with Z-Modem. If the file doesn't make
it, you have a "dirty" link).
One thing you might try is run Slirp as:
slirp "asyncmap ffffffff" "escape ff"
(quotes included!) This will tell Slirp to escape the most common
"nasty characters.
Symptom:
You can connect to hosts using numerical addresses (of the form
aa.bb.cc.dd) but you cannot connect to hosts when you use their
hostname (E.g.: ftp.cdrom.com). It usually times out with a DNS
error.
Diagnosis:
You probably did not set your DNS address properly.
Cure:
Try setting your DNS address to 10.0.2.3. This should work for
most situations. If that fails, go to your shell prompt and type
"nslookup". This should print the address and hostname of your
DNS server. Use the numerical IP address as your DNS. Do NOT
use the hostname.
If you still can't find your DNS address, ask your sysadmin for
it.
Answers to Frequently Asked Questions (FAQs)
Q1. Can I use Slirp through Telnet or Rlogin?
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A1. Yes, usually. But this is highly dependent on your situation.
The reason Slirp usually doesn't work through telnet is because
of the ^] character is interpreted by the telnet client, and 0xff
interpreted by the server. While you can tell Slirp to escape
these characters while using PPP, it may not be possible to get
your local PPP software to escape characters greater than ASCII
31. Rlogin also interprets the ~ character, which may interfere
with PPP (especially considering ~ is ASCII 0x7e which is used by
PPP as the "end of packet" character").
If your PPP software is unable to escape these characters, or
you're using (C)SLIP (which must have an 8bit clean link), your
best bet is to try and make the link 8bit clean. For example, on
some systems you can give telnet the -8 flag to make the link
8bit, and -E to stop it from interpreting the ^] character.
Similarly for rlogin; -8 to make the link 8bit, -E to stop rlogin
from interpreting the ~ character. You should look at the telnet
and rlogin manual pages ("man telnet" and "man rlogin"
respectively) to see if your telnet/rlogin has similar options.
Another possible solution is to use Slirp's ability to work over
multiple hosts. See the slirp.doc documentation for more
details.
Q2. How do I run an X program on another host and have it display on
my PC?
A2. Use the "redir X" command in ~/.slirprc. This will redirect a
port for use with X programs.
On startup, Slirp should print something like:
X Redir: In sh/bash/zsh/etc. type: DISPLAY=IP.ADDRESS:X.Y; export DISPLAY
X Redir: In csh/tcsh/etc. type: setenv DISPLAY IP.ADDRESS:X.Y
Now, when you telnet to the host you wish to run the X programs
from, you should do as Slirp suggest above; type either of the
two commands, depending on which shell you are using. You could
also run the X program as "xprog -display IP.ADDRESS:X.Y" as
printed above.
If you missed what Slirp displayed on startup, you can telnet to
10.0.2.0 and give Slirp the command "show X", and the above will
be printed.
Note that you also have to make sure your X server will accept
the connection. See the man page for xhost and Xsecurity. Be
careful with issuing commands like "xhost +", this will allow
anyone to connect to your X server and do basically anything they
want.
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Q3. When I run "talk" or "wintalk", etc. I am able to send requests
to other people but they cannot send requests to me. Why?
A3. You won't be able to receive talk requests, period. This is
because Slirp never see's the incoming talk request; it is sent
directly over the modem, most likely corrupting any incoming
packet with it (which will have to be retransmitted). Slirp
turns off your messages so the person who tries to talk to you
should receive a "User is refusing messages" error.
Q4. I can't telnet to 10.0.2.0, the Slirp control address. What's
wrong?
A4. See the answer to this question in slirp.doc and recompile slirp.
Q5. I'm having a few problems with Slirp and want to try and find the
problem myself. Does Slirp have any debugging facilities?
A5. Yes. See slirp.doc for compile-time debug options.
Q6. My ISP logs me out if I idle too long. How can I get Slirp to
prevent this?
A6. First of all, the idle-logout mechanism is used for a reason: to
prevent people from hogging a modem which is not in use. So if
you're idle, logout and give others chance to logon.
Having said that, you can make Slirp use TCP keep-alive timers to
regularly probe each TCP connection. To activate this, add:
keepalive
to your ~/.slirprc file. This will make Slirp probe each TCP
connection every minute or so. You can change this interval by
giving keepalive the number of seconds:
keepalive SECONDS
Note that no probes will be sent if there are no TCP connections.
So you need at least one active TCP connection for this to work.
GETTING HELP
There are several sources of help. First, read the previous sections
"Troubleshooting" and "Answers to Frequently Asked Questions (FAQs)".
If that fails, try the Slirp Home Page at:
http://blitzen.canberra.edu.au/slirp
There are lots of neat links there to other pages which have specific
configuration information.
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There is also a Newsgroup dedicated to SLIP-emulators called
alt.dcom.slip-emulators. You will find lots of discussion about Slirp
and other "SLIP-emulators". The FAQ (Frequently Asked Questions) for
alt.dcom.slip-emulators is included in the "docs" directory, I would
suggest reading this as well.
If all else fails, send me e-mail to danjo@blitzen.canberra.edu.au
with the following information:
* Output of the command "uname -a" on the remote system;
* Operating System name and version you run on your PC;
* Version of Slirp you are using (IMPORTANT!!!);
* If you managed to get Slirp running, run Slirp as "slirp -S" then
try whatever failed. When you exit Slirp, you should have a file
called "slirp_stats". Send me this file; and
* Anything else you consider relevant.
*PLEASE* include all the above information. If you do not, I may
simply press "d". I can't guarantee a response, but I will try my
best.
THANKS
A big "THANK YOU!" goes to the following people for their help in
creating Slirp.
Juha Pirkola, Gregory M. Christy, The Regents of the University of
California, Carnegie Mellon University, The Australian National
University, and RSA Data Security, Inc. whose source code is used
throughout Slirp. Slirp would not be without them.
Thanks to all the contributors who helped with bugs, suggestions,
code, etc. Read the file ChangeLog to see exactly who helped with
what.
A special thanks goes to Chris Metcalf and Juha Pirkola for their
contributions (see ChangeLog). They put in extra effort and Slirp
wouldn't be the same without their help. Thanks guys!
Thanks to all the people who sent very kind and encouraging e-mail,
it's sincerely appreciated.
Thanks to all the admins and Head Honcho's at UCNet, the University of
Canberra Computer Club ("blitzen") who gave me some real-estate on
their machine (blitzen.canberra.edu.au) to work with (thanks to Tony
Delroy for giving me the account originally). Hey! Why don't you
check out their home page at http://blitzen.canberra.edu.au/?
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Thanks to Brazil for coffee (and Sepultura! :)
Thanks to the laws of physics, the building blocks of the universe.
COPYRIGHT
Slirp was written by Danny Gasparovski.
Copyright (c) 1995 Danny Gasparovski. All Rights Reserved.
Slirp is free software; "free" as in you don't have to pay for it, and
you are free to do whatever you want with it. I do not accept any
donations, monetary or otherwise, for Slirp. Instead, I would ask you
to pass this potential donation to your favorite charity. In fact, I
encourage *everyone* who finds Slirp useful to make a small donation
to their favorite charity (for example, GreenPeace). This is not a
requirement, but a suggestion from someone who highly values the
service they provide.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the
distribution.
3. All advertising materials mentioning features or use of this
software must display the following acknowledgment: This product
includes software developed by Danny Gasparovski.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL DANNY GASPAROVSKI OR CONTRIBUTORS BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
This basically means you can do anything you want with the software,
except 1) call it your own, and 2) claim warranty on it. There is no
warranty for this software. None. Nada. If you lose a million
dollars while using Slirp, that's your loss not mine. So, ***USE AT
YOUR OWN RISK!***.
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9 Jan 1996
If these conditions cannot be met due to legal restrictions (E.g.
where it is against the law to give out Software without warranty),
you must cease using the software and delete all copies you have.
Slirp uses code that is copyrighted by the following
people/organizations:
Juha Pirkola.
Gregory M. Christy.
The Regents of the University of California.
Carnegie Mellon University.
The Australian National University.
RSA Data Security, Inc.
Please read the top of each source file for the details on the various
copyrights.
AUTHOR
Slirp was written by Danny Gasparovski.
Manpage by George Ferguson, ferguson@cs.rochester.edu, based on Slirp
1.0b documentation.
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