tcpserver(1)                         General Commands Manual                         tcpserver(1)



NAME
       tcpserver - accepts incoming TCP connections.

SYNOPSIS
       tcpserver [ opts ] host port prog

DESCRIPTION
       opts  is  a  series of getopt-style options.  host is one argument.  port is one argument.
       prog consists of one or more arguments.

       tcpserver waits for connections from TCP clients. For each connection, it runs prog,  with
       descriptor  0  reading  from  the network and descriptor 1 writing to the network. It also
       sets up several environment variables.

       The server's address is given by host and port.  port may be a name from /etc/services  or
       a number; if it is 0, tcpserver will choose a free TCP port.  host may be 0, allowing con‐
       nections to any local IP address; or a dotted-decimal  IP  address,  allowing  connections
       only  to  that  address;  or a host name, allowing connections to the first IP address for
       that host. Host names are fed through qualification using dns_ip4_qualify.

       tcpserver exits when it receives SIGTERM.

OPTIONS
       General options:

       -q     Quiet. Do not print error messages.

       -Q     (Default.) Print error messages.

       -v     Verbose. Print error messages and status messages.

       Connection options:

       -c n   Do not handle more than n simultaneous connections. If  there  are  n  simultaneous
              copies  of  prog  running, defer acceptance of a new connection until one copy fin‐
              ishes.  n must be a positive integer. Default: 40.

       -x cdb Follow the rules compiled into cdb by tcprules(1).  These rules may specify setting
              environment  variables  or  rejecting  connections  from bad sources. You can rerun
              tcprules(1) to change the rules while tcpserver is running.

       -X     With -x cdb, allow connections even if cdb does not exist. Normally tcpserver  will
              drop the connection if cdb does not exist.

       -B banner
              Write  banner  to the network immediately after each connection is made.  tcpserver
              writes banner before looking up $TCPREMOTEHOST, before looking  up  $TCPREMOTEINFO,
              and  before  checking cdb.  This feature can be used to reduce latency in protocols
              where the client waits for a greeting from the server.

       -g gid Switch group ID to gid after preparing to receive connections.  gid must be a posi‐
              tive integer.

       -u uid Switch  user ID to uid after preparing to receive connections.  uid must be a posi‐
              tive integer.

       -U     Same as -g $GID -u $UID. Typically $GID and $UID are set by envuidgid(8).

       -1     After preparing to receive connections, print the local  port  number  to  standard
              output.

       -b n   Allow a backlog of approximately n TCP SYNs. On some systems, n is silently limited
              to 5. On systems supporting SYN cookies, the backlog is irrelevant.

       -o     Leave IP options alone. If the client is sending packets along an IP source  route,
              send packets back along the same route.

       -O     (Default.) Kill IP options. A client can still use source routing to connect and to
              send data, but packets will be sent back along the default route.

       -d     Delay sending data for a fraction of a second whenever the remote host is  respond‐
              ing  slowly. This is currently the default, but it may not be in the future; if you
              want it, set it explicitly.

       -D     Never delay sending data; enable TCP_NODELAY.

       Data-gathering options:

       -h     (Default.) Look up the remote host name in DNS  to  set  the  environment  variable
              $TCPREMOTEHOST.

       -H     Do not look up the remote host name in DNS; remove the environment variable $TCPRE‐
              MOTEHOST. To avoid loops, you must use this option for servers on TCP port 53.

       -p     Paranoid. After looking up the remote host name in DNS, look up the IP addresses in
              DNS  for that host name, and remove the environment variable $TCPREMOTEHOST if none
              of the addresses match the client's IP address.

       -P     (Default.) Not paranoid.

       -l localname
              Do not look up the local host name in DNS; use localname for the environment  vari‐
              able  $TCPLOCALHOST.  A  common choice for localname is 0. To avoid loops, you must
              use this option for servers on TCP port 53.

       -r     (Default.) Attempt to obtain $TCPREMOTEINFO from the remote host.

       -R     Do not attempt to obtain $TCPREMOTEINFO from the remote host. To avoid  loops,  you
              must use this option for servers on TCP ports 53 and 113.

       -t n   Give up on the $TCPREMOTEINFO connection attempt after n seconds. Default: 26.

SEE ALSO
       tcprules(1),   tcprulescheck(1),  argv0(1),  fixcrio(1),  recordio(1),  rblsmtpd(1),  tcp‐
       client(1), who@(1), date@(1), finger@(1), http@(1), tcpcat(1), mconnect(1), tcp-environ(5)

       http://cr.yp.to/ucspi-tcp.html



                                                                                     tcpserver(1)