Provided by: slirp_1.0.17-8_amd64 bug


       slirp - TCP/IP emulator


       slirp [options|commands]
       slirp help
       slirp "help cmd"


       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!


       To run Slirp, simply type:


       (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

       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.

       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.


       Slirp can be configured in 3 different ways: the command line,  the  configuration  files,
       and  "on-the-fly"  configuration by telnet-ing to 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:

           -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:
               -b 14400
               redir 5022 21

           Command line:
               slirp -P -b 14400 "redir 5022 21"

       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;  if  it
       was in a telnet, then the IP address used is the IP address from where the telnet connection was made. For example, if you  have  a  LAN  at  home  and  telnet  to  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 connection. Also, if  you  use  an  IP
       address  on  your  PC  other than, 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 -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).


       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 and type:


       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

       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

             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.

                 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 when in
                 ~/.slirprc, the source IP address when in command-line).

                 Which display to redirect to (default :0).

                 Which screen to redirect to (default .0).

           Example: redir X

           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

           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

             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]

             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

           Note: if this command is in your .slirprc file and no address is  specified,  it  will
           assume  that  your  local  IP  address is 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

             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

           Note: The ADDRESS for special must end in 0 (zero) and  other  addresses  are  classed
           from this.  The default special address is giving the following defined IP's:

                 slirp control telnet IP
                 slirp exec IP
                 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 connect to ADDRESS at
           port PORT.
           Usable: anywhere

             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 will start and connect you
           directly to the csh program on the host. (telnet 55).

           Example: add exec nntpd:
           A program that attempts to open port 119 at address 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).

           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.

           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

       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.

             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.

                    Can be: ftp, ksh, irc, none.

                    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

           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

       dns DNS_IP
           Give  this to slirp if you want to use as an alias for DNS, AND slirp guesses
           wrong for the DNS on startup.


 Special Addresses
       All addresses of the form are special to Slirp (this can be  changed  with  the
       "special  addr"  command).   The  following is a description of what each of the addresses
              This is the Slirp "on-line" configuration address.  When you telnet to 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  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  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 (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
      as  the  News  host  and  it will actually connect to the running program
              This is an alias for the remote host.   When  you  connect  to  you  will
              actually  connect  to  the  host Slirp is running on.  This is useful if your shell
              account can be on different hosts, will always  mean  the  host  Slirp  is
              running on.
              This  is  an alias for your DNS.  Slirp will try to figure out your DNS address and
              all data sent to will be redirected to your DNS address, so you  can  tell
              your  TCP/IP software to use 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.
              This is the address recommended by Slirp to be used on your PC.   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

           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:

           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, is assumed.

          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))

          redir udp 22555 YOUR_PC_ADDRESS:22555

          redir udp 8000 YOUR_PC_ADDRESS:8000
          (the 8000 is configurable)

          redir tcp 13223 YOUR_PC_ADDRESS:13223

          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

       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.

       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

       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  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.

       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.


 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:

            irc (for /dcc)

              The  connection  will  "freeze".   E.g., while downloading a picture on WWW it will
              stop halfway and no connections will continue.

               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

              You  can  connect  to hosts using numerical addresses (of the form but
              you cannot connect to hosts when you use their hostname (E.g.:   It
              usually times out with a DNS error.

              You probably did not set your DNS address properly.

       Cure:  Try  setting  your  DNS address to  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?

       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"

              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

              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 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.

       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, 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:


              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

                  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.


       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:


       There are lots of neat links there  to  other  pages  which  have  specific  configuration

       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  with  the  following

         * 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;

         * 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.


       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

       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 (
       to work with (thanks to Tony Delroy for giving me the account originally).  Hey! Why don't
       you check out their home page at

       Thanks to Brazil for coffee (and Sepultura! :)

       Thanks to the laws of physics, the building blocks of the universe.


       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


       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!***.

       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.


       Slirp was written by Danny Gasparovski.

       Manpage by George Ferguson,, based on Slirp 1.0b documentation.