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    Command:

    faucet

    
           netpipes 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
    
    
    

    DESCRIPTION

           faucet attempts to provide the functionality of pipes over the network.
           It  behaves as the server end of a server-client connection.  When used
           with hose(1) it can function as a replacement for
    
           tar -cf - . | rsh other "cd destdir; tar -xf -"
    
           faucet and  hose  are  especially  useful  when  you  don't  have  easy
           non-interactive  access  to  the  destination  account  (such as a root
           account where .rhosts are a bad idea).
    
           faucet creates a BSD socket, binds it to the port specified on the com-
           mand line, and listens for connections.
    
           Every  time  faucet  gets a connection it exec(2)s command and its args
           with stdin, stdout, stderr, and/or  arbitrary  file  descriptors  redi-
           rected  according  to  the  --in --out --err --fd n flags.  faucet also
           automagically shuts down the unused half of the connection if only --in
           is  specified  or  if  only  --out and/or --err are specified.  See the
           --shutdown option for more information.
    
    
    

    OPTIONS

           If the --once flag  is  specified,  faucet  will  exec(2)  the  command
           instead  of  fork(2)ing  and exec(2)ing.  --once means that the network
           pipe is only good for one shot.
    
           The --verbose flag specifies that faucet should print information about
           connecting  hosts.  This information includes the numeric host address,
           host names, and foreign port numbers.  The --quiet flag specifies  that
           faucet should NOT print such info.  --quiet is the default.
    
           The  --unix flag specifies that the port is not an internet port number
           or service name, but instead it is  a  file  name  for  a  UNIX  domain
           socket.
    
           The  --foreignhost  option specifies that faucet should reject all con-
           nections that do not come from the host machine.  Similarly  --foreign-
           port  specifies  that faucet should reject all connections that are not
           bound on their local machine to  the  port  argument.   The  above  two
           trolling terminal once it has started listening on the socket.  This is
           done using the setsid() system call.  If you don't have setsid on  your
           system,  it uses the standard ''close all file descriptors, ioctl TIOC-
           NOTTY, fork() and parent exit'' sequence.
    
           --shutdown is used to turn the (normally) bi-directional socket into  a
           uni-directional  one If the 'r' is present, then faucet will close half
           the connection to make it a read-only socket.  If we try to  write,  it
           will  fail.   If  the remote connection tries to read, it will percieve
           the socket as closed.  If instead the 'w' is present, then faucet  will
           close  the other half of the connection to make it a write-only socket.
           If we try to read, we will percieve  the  socket  as  closed.   If  the
           remote  connection  tries to write, it will fail.  The default behavior
           is to leave both halves open, however the shutdown of half of the  con-
           nection  is  automagically  done  by  certain combinations of the --in,
           --out, and --err flags.  To suppress their automagic behavior  you  can
           use (respectively) --fd 0, --fd 1, and --fd 2.
    
           --shutdown  may not be used with some internet servers (such as certain
           httpds) because they interpret the closing of one half of  the  connec-
           tion  as  a  close  on  the entire connection.  This warning applies to
           --in, --out, and --err.
    
           --serial causes faucet to wait for one child to finish before accepting
           any  more  connections.   Serialization  is a very crude form of criti-
           cal-section management.
    
           --pidfile filename commands faucet to write its process id  into  file-
           name.  This is useful when faucet is part of a larger system and a con-
           trolling process might want to kill the  faucet.   --pidfile  functions
           properly when using the --daemon  option.
    
           By default, faucet performs a
    
           setsockopt(fd, SOL_SOCKET, SO_REUSEADDR...)
    
           which prevents the ''Address in use'' problem that ''plagued'' netpipes
           versions 4.0 and earlier.  --noreuseaddr tells faucet to skip that sys-
           tem  call,  and  revert  to  pre-4.1  behavior.  Without this call, the
           socket is not always available for immediate  reuse  after  the  faucet
           exits.
    
           --backlog n allows you to specify the second parameter to the listen(2)
           system call.  The default is 5.
    
    
    

    SHORT FLAGS

           To reduce the typing requirements for arguments (and to pay  homage  to
           the  age-old  tradition of UNIX cryptotaxonomy) I have added some short
           forms of the flags.  Here is a correspondence chart:
    
           |  H   | localhost    |
           +------+--------------+
           For example, the following command
    
           example$ faucet 3000 --out --verbose --once --foreignhost client echo blah
    
           could be written
    
           example$ faucet 3000 -ov1h client echo blah
    
           The -p, -h, and -H flags take an argument, but the flags may be grouped
           into  one  argument.   They  then grab the arguments they need from the
           command line in the order the flags appear.
    
           example$ faucet 3000 -hpHov1 client 2999 example-le2 echo blah
    
           Whereas each --fd word flag required an individual descriptor,  the  -#
           character flag can take multiple descriptors.  The following are equiv-
           alent:
    
           example$ faucet 3000 --fd 0 --fd 1 --verbose --once echo blah
           example$ faucet 3000 -#0,1v --once echo blah
           example$ faucet 3000 -v1#0,1 echo blah
           example$ faucet 3000 -#0,1v1 echo blah
    
           Note that you have to pay attention when using the  -#  character  flag
           and  the  -1  character  flag in the same argument.  Also, remember the
           special shutdown(2) semantics of -in and -out.
    
    
    

    EXAMPLES

           This creates a TCP-IP socket on the local machine bound to port 3000.
    
           example$ faucet 3000 --out --verbose tar -cf - .
    
           Every time some process (from any machine) attempts to connect to  port
           3000  on this machine the faucet program will fork(2) a process and the
           child will exec(2) a
    
           tar -cf - .
    
           The --out option means that the output of the child process  will  have
           been  redirected  into  the new socket retrieved by the accept(2) call.
           --verbose means that faucet will print information about each new  con-
           nection.
    
           This creates a UNIX domain socket in the current directory
    
           example$ faucet u-socket --out --err --once --unix csh -c \
                 "dd if=angio.pgm | funky.perl.script"
    
           The  --out --err option means that stdout and stderr will be redirected
           (3)
    
    
    

    BUGS

           There is a problem with almost every OS I have used faucet  on.   Ports
           are  sometimes not recycled swiftly enough.  If you kill one faucet and
           try to start another that wants to listen on the  same  port  you  will
           often  see  pre-4.1  faucets  print the following warning over and over
           again:
    
           faucet: Address 3000 in use, sleeping 10.
           faucet: Trying again . . .
    
           but you won't actually  be  able  to  connect(2)  to  that  port  (with
           hose(1), for example) because you'll get a ''connection refused''.
    
           There  was  also an experimental Linux kernel that NEVER recycled ports
           (I quickly switched back to my old kernel).
    
           I have been informed that this is a side-effect of the  TCP  specifica-
           tion  and  that I should use the SO_REUSEADDR option to work around it,
           so I do.
    
    
    

    NOTES

           Doubtless there are bugs in this program, especially in the unix domain
           socket  portions.   I  welcome  problem  reports and would like to make
           these programs as "clean" (no leftover files, sockets) as possible.
    
           4.1 added --backlog and --noreuseaddr.  --noreuseaddr reflects the fact
           that 4.1 also added the SO_REUSEADDR socket option as the default.
    
           4.0  made  the full-word arguments use -- like many GNU programs.  They
           are still available with a single - for backward-compatibility.
    
           3.1 added the single-character flags and the -pidfile option.  It  also
           switched to the setsid(2) system call to detach itself from the process
           group for the -daemon flag.  I've been hacking at UNIX for  years,  but
           there  are  still  some  things that I never really learned, and others
           that have been changing.  I need to buy a book.
    
           Release 2.3 added support for multi-homed hosts:  hosts  with  multiple
           internet  numbers  (such as gateways).  Before this faucet assumed that
           the first internet number that gethostbyname returned was the only one.
           --foreignhost  authentication  was  weakened  by  this  inadequacy so I
           beefed up the algorithms.  --foreignhost will accept a connection  from
           any of the internet numbers associated with the host name.
    
    
    

    CREDITS

           Thanks to Steve Clift <clift@ml.csiro.au> for SGI (SysV) patches.
    
           gesting the -pidfile flag.
    
           Big  thanks to Joe Traister <traister@gate.net> for his signal handling
           patches, strerror surrogate, and other assorted hacks.
    
           Thanks to Thomas A. Endo <tendo@netcom.com> for dropping  an  SO_REUSE-
           ADDR  patch  in  my  lap.   Otherwise I wouldn't have gotten to it till
           2001.
    
    
    

    COPYRIGHT

           Copyright (C) 1992-98 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.
    
    
    

    AUTHOR

           Robert Forsman
            thoth@purplefrog.com
            Purple Frog Software
            http://web.purplefrog.com/~thoth/
    
                                   October 28, 1998                      FAUCET(1)
    
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