NETPIPES(1) General Commands Manual NETPIPES(1)
NAME
netpipes - a package to manipulate BSD TCP/IP stream sockets
version 4.2
SYNOPSIS
faucet port (--in|--out|--err|--fd n)+ [--once] [--verbose] [--quiet] [--unix] [--foreignhost addr] [--foreignport port] [--localhost addr]
[--serial] [--daemon] [--shutdown (r|w) ] [--pidfile filename] [--noreuseaddr] [--backlog n] [-[i][o][e][#3[,4[,5...]]][v][1][q][u][d][s]]
[-p foreign-port] [-h foreign-host] [-H local-host] command args
hose hostname port (--in|--out|--err|--fd n|--slave) [--verbose] [--unix] [--localport port] [--localhost addr] [--retry n] [--delay n]
[--shutdown [r|w][a] ] [--noreuseaddr] [-[i][o][e][#3[,4[,5...]]][s][v][u]] [-p local-port] [-h local-host] command args
encapsulate --fd n [ --verbose ] [ --subproc [ --infd n[=sid] ] [ --outfd n[=sid] ] [ --duplex n[=sid] ] [ --Duplex n[=sid] ] [ --DUPLEX
n[=sid] ] [ --prefer-local ] [ --prefer-remote ] [ --local-only ] [ --remote-only ] ] [ --client ] [ --server ]
-[#n][v][s[in][on][dn][ion][oin][l][r][L][R]] command args ...
sockdown [fd [how] ]
getpeername [ -verbose ] [ -sock ] [ fd ]
getsockname [ -verbose ] [ -peer ] [ fd ]
timelimit.netpipes [ -v ] [ -nokill ] time command args
DESCRIPTION
The netpipes package makes TCP/IP streams usable in shell scripts. It can also simplify client/server code by allowing the programmer to
skip all the tedious programming bits related to sockets and concentrate on writing a filter/service.
``Why would anyone want to do that?''
-- Richard Stallman
faucet is the server end of a TCP/IP stream. It listens on a port of the local machine waiting for connections. Every time it gets a con-
nection it forks a process to perform a service for the connecting client.
hose is the client end of a TCP/IP stream. It actively connects to a remote port and execs a process to request a service.
encapsulate is an implementation of the Session Control Protocol. It allows you to multiplex several streams across a single TCP session
and also transmits remote exit status.
sockdown is a simple program designed to shut down part or all of the socket connection. It is primarily useful when the processes con-
nected to the socket perform both input and output.
getpeername and getsockname are two names for a program designed to print out the addresses of the ends of a socket. getpeername prints
the address of the remote end and getsockname prints the address of the local end.
timelimit.netpipes limits the amount of foreground wallclock time a process may consume. After the time limit runs out, it either kills
the process, or exits and leaves it in the background.
EXAMPLES
Here is a simple command I often perform to transfer directory trees between machines. (rsh does not work because one machine is connected
using SLIP and .rhosts are out of the question).
server$ faucet 3000 --out tar cf - .
client$ hose server 3000 --in tar xvf -
Here is a minimal HTTP client. It is so minimal it speaks old HTTP.
cairo$ hose www.cis.ufl.edu 80 --in --out
sh -c "(echo 'GET /'; sockdown) & cat > result"
And of course, there is Nick Trown's metaserver for Netrek
cairo$ hose metaserver.ecst.csuchico.edu 3521 --in cat
Allow me to apologize ahead of time for the convolutedness of the following example. It requires an understanding of Bourne shell file
descriptor redirection syntax (and illustrates why csh and tcsh suck eggs). Do not try to type this from your tcsh command line. Get a
bash (GNU's Bourne Again SHell).
Suppose you want to distinguish between stdout and stderr of a remote process
remote$ faucet 3000 --fd 3
encapsulate --fd 3 --infd 0 --outfd 1 --outfd 2 --subproc
remote-app
local$ hose remote 3000 --fd 3
encapsulate --fd 3 --outfd 3 --infd 4 --infd 5 --subproc
sh -c "cat 0<&4 3>&- & cat 0<&5 1>&2 3>&- &
cat 1>&3 ; exec 3>&-"
Close all unneeded file descriptors when you spawn a background task. That's why the backgrounded cats have 3>&-.
server$ faucet 3000 --in --out --verbose enscript -2rGhp -
client$ ps aux | hose server 3000 --in --out
sh -c " (cat <&3; sockdown ) & cat >&4 " 3<&0 4>&1 |
lpr -Pps422
#or perhaps this, but I haven't tested it
client$ ps aux | hose server 3000 --fd 3
sh -c " (cat >&3; sockdown 3 ) & cat <&3 " |
lpr -Pps422
This proves that hose can be used as part of a pipeline to perform a sort of remote procedure call (RPC). After you have figured out that
example, you will know how to use Bourne shell to shuffle file descriptors around. It is a handy skill.
Now we go to the extreme, but simplify things by using the --slave option of hose. The following is a socket relay
gateway$ faucet 3000 -io hose server 4000 --slave
It's a handy little bugger when you want to tunnel through a firewall on an occasional basis. If you experience ``hanging'' of the connec-
tion, try using the --netslave option instead of --slave. (telnet proxies would benefit from this)
For those of you who use ssh, here's how to tunnel some information through an encrypted SSH port forward.
server$ faucet 3000 -1v --fd 1 --foreignhost server echo blah
client$ ssh -n -x -L 3000:server:3000 server sleep 60 &
client$ hose localhost 3000 --fd 0 -retry 10 cat
The trick with ssh's port forwarding, is that the shutdown(2) system call causes ssh to close both halves of the full-duplex connection
instead of only one half. That's why you have to use --fd 1 and --fd 0. If you need to be able to close half of the connection while
still using the other, use the encapsulate wrapper.
server$ faucet 3000 -1v --fd 3 --foreignhost server
encapsulate --fd 3 --server -si0o1 tr a-z A-Z
client$ ssh -n -x -L 3000:server:3000 server sleep 60 &
client$ echo blah | hose localhost 3000 --fd 3 -retry 10
encapsulate --fd 3 --client
REMARK
The Debian package maintainer has renamed timelimit to the more expressive timelimit.netpipes, as there exists a better alternative using
the same short name, but which is actively maintained as an independent software.
SEE ALSO
faucet(1), hose(1), encapsulate(1), sockdown(1), getpeername(1), timelimit.netpipes(1), timelimit(1).
BUGS
Report any bugs or feature requests to thoth@purplefrog.com
CREDITS
Thanks to Harbor Development Inc. for funding some of the netpipes development.
Thanks to Michal Jaegermann <michal@ellpspace.math.ualberta.ca> for some bug fixes and glibc portability suggestions against 4.1.1 .
Big thanks to Joe Traister <traister@gate.net> for his signal handling patches, strerror surrogate, and other assorted hacks.
COPYRIGHT
Copyright (C) 1995-98 Robert Forsman
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MER-
CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation,
Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
DOWNLOAD
Export Version: ftp://ftp.purplefrog.com/pub/netpipes/
U.S./Canada version with ssl-auth: http://www.cryptography.org/ , then find it in the network/ subdirectory.
AUTHOR
Robert Forsman
thoth@purplefrog.com
Purple Frog Software
http://web.purplefrog.com/~thoth/
October 28, 1997 NETPIPES(1)