bionic (1) tcpserver.1.gz

NAME

       tcpserver - accept incoming TCP connections

SYNOPSIS

       tcpserver [ -146jpPhHrRoOdDqQv ] [ -climit ] [ -xrules.cdb ] [ -Bbanner ] [ -ggid ] [ -uuid ] [ -bbacklog
       ] [ -llocalname ] [ -ttimeout ] [ -Iinterface ] host port program [ arg ...  ]

DESCRIPTION

       tcpserver waits for connections from TCP clients.  For each connection, it runs program  with  the  given
       arguments, with descriptor 0 reading from the network and descriptor 1 writing to the network.

       The  server's address is given by host and port.  host can be 0, allowing connections from any host; or a
       particular IP address, allowing connections only to that address; or a host name, allowing connections to
       the  first  IP  address  for that host.  port may be a numeric port number or a port name.  If port is 0,
       tcpserver will choose a free port.

       tcpserver sets up several environment variables, as described in tcp-environ(5).

       tcpserver exits when it receives SIGTERM.

OPTIONS

       -climit
              Do not handle more than limit simultaneous connections.  If there are limit simultaneous copies of
              program  running,  defer  acceptance of a new connection until one copy finishes.  limit must be a
              positive integer.  Default: 40.

       -xrules.cdb
              Follow the rules compiled into rules.cdb by tcprules.  These rules may specify setting environment
              variables or rejecting connections from bad sources.

              tcpserver  does  not  read  rules.cdb  into  memory;  you can rerun tcprules to change tcpserver's
              behavior on the fly.

       -Bbanner
              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 rules.cdb.

              This feature can be used to reduce latency in protocols where the client waits for a greeting from
              the server.

       -ggid  Switch group ID to gid after preparing to receive connections.  gid must be a positive integer.

       -uuid  Switch user ID to uid after preparing to receive connections.  uid must be a positive integer.

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

       -4     Fall back to IPv4 sockets.  This is necessary for terminally broken  systems  like  OpenBSD  which
              will not let IPv6 sockets connect to V4-mapped IPv6 addresses.  Please note that this also applies
              to DNS lookups, so you will have to use an DNS resolver  with  an  IPv6  address  to  accept  IPv6
              connections.  Use DNSCACHEIP to set the DNS resolver IP dynamically.

       -6     Force  IPv6  mode in UCSPI environment variables, even for IPv4 connections.  This will set $PROTO
              to TCP6 and put IPv4-mapped IPv6 addresses in TCPLOCALIP and TCPREMOTEIP.

       -Iinterface
              Bind to the network interface interface ("eth0" on Linux, for example).  This is only defined  and
              needed for IPv6 link-local addresses.

       -bbacklog
              Allow  up  to  backlog  simultaneous  SYN_RECEIVEDs.   Default:  20.   On some systems, backlog is
              silently limited to 5.  See listen(2) for more details.

       -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     (Default.)  Delay sending data for a fraction of a second whenever the remote host  is  responding
              slowly, to make better use of the network.

       -D     Never delay sending data; enable TCP_NODELAY.  This is appropriate for interactive connections.

       -q     Quiet.  Do not print any messages.

       -Q     (Default.)  Print error messages.

       -v     Verbose.  Print all available messages.

DATA-GATHERING OPTIONS

       -p     Paranoid.  After looking up the remote host name, look up the IP addresses for that name, and make
              sure one of them matches TCPREMOTEIP.  If none of them do, unset TCPREMOTEHOST.

       -P     (Default.)  Not paranoid.

       -h     (Default.)  Look up the remote host name and set TCPREMOTEHOST.

       -H     Do not look up the remote host name.

       -llocalname
              Do not look up the local host name; use localname for TCPLOCALHOST.

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

       -R     Do not attempt to obtain TCPREMOTEINFO from the remote host.

       -ttimeout
              Give up on the TCPREMOTEINFO connection attempt after timeout seconds. Default: 26.

SEE ALSO

       argv0(1), fixcr(1), recordio(1), tcpclient(1), tcprules(1), listen(2), tcp-environ(5)

                                                                                                    tcpserver(1)