NAME

       tcpsvd - TCP/IP service daemon

SYNOPSIS

       tcpsvd [-hpEvv] [-c n] [-C n:msg] [-b n] [-u user] [-l name] [-i dir|-x cdb] [ -t sec] host port prog

DESCRIPTION

       tcpsvd creates a TCP/IP socket, binds it to the address host:port, and listens on the socket for incoming
       connections.

       On each incoming connection, tcpsvd conditionally runs a program, with standard input  reading  from  the
       socket,  and standard output writing to the socket, to handle this connection.  tcpsvd keeps listening on
       the socket for new connections, and can handle multiple connections simultaneously.

       tcpsvd optionally checks for special instructions depending on the IP address or hostname of  the  client
       that initiated the connection, see ipsvd-instruct(5).

OPTIONS

       host   host  either  is  a  hostname, or a dotted-decimal IP address, or 0.  If host is 0, tcpsvd accepts
              connections to any local IP address.

       port   tcpsvd accepts connections to host:port.  port may be a name from /etc/services or a number.

       prog   prog consists of one or more arguments.  For each connection, tcpsvd normally runs prog, with file
              descriptor  0  reading from the network, and file descriptor 1 writing to the network.  By default
              it also sets up TCP-related environment variables, see tcp-environ(5)

       -i dir read instructions for handling new connections from the instructions directory  dir.   See  ipsvd-
              instruct(5) for details.

       -x cdb read  instructions  for  handling  new  connections  from the constant database cdb.  The constant
              database normally is created from an instructions directory by running ipsvd-cdb(8).

       -t sec timeout.  This option  only  takes  effect  if  the  -i  option  is  given.   While  checking  the
              instructions directory, check the time of last access of the file that matches the clients address
              or hostname if any, discard and remove the file if it wasn't accessed within the last sec seconds;
              tcpsvd  does  not  discard  or  remove a file if the user's write permission is not set, for those
              files the timeout is disabled.  Default is 0, which means that the timeout is disabled.

       -l name
              local hostname.  Do not look up the local hostname in DNS, but use name as hostname.  This  option
              must be set if tcpsvd listens on port 53 to avoid loops.

       -u [:]user[:group]
              drop  permissions.   Set  uid  and  gid to the user's uid and gid, as found in /etc/passwd, before
              running prog.  If user is followed by a colon and a group, set the gid to group's gid, as found in
              /etc/group,  instead  of  user's gid.  If group consists of a colon-separated list of group names,
              set the group ids of all listed groups.  If user is prefixed with a colon, the user and all  group
              arguments are interpreted as uid and gids respectively, and not looked up in the password or group
              file.  All supplementary groups are removed.

       -c n   concurrency.  Handle up to  n  connections  simultaneously.   Default  is  30.   If  there  are  n
              connections  active,  tcpsvd  defers  acceptance of a new connection until an active connection is
              closed.

       -C n[:msg]
              per host concurrency.  Allow only up to n connections from the same IP address simultaneously.  If
              there  are n active connections from one IP address, new incoming connections from this IP address
              are closed immediately.  If n is followed by :msg, the message msg is written  to  the  client  if
              possible,  before  closing  the  connection.   By default msg is empty.  See ipsvd-instruct(5) for
              supported escape sequences in msg.

              For each  accepted  connection,  the  current  per  host  concurrency  is  available  through  the
              environment  variable  TCPCONCURRENCY.  n and msg can be overwritten by ipsvd(7) instructions, see
              ipsvd-instruct(5).  By default tcpsvd doesn't keep track of connections.

       -h     Look up the client's hostname in DNS.

       -p     paranoid.  After looking up the client's hostname in DNS, look up the IP addresses in DNS for that
              hostname,  and  forget  about the hostname if none of the addresses match the client's IP address.
              You should set this option if you use hostname based instructions.  The -p option implies  the  -h
              option.

       -b n   backlog.   Allow  a  backlog  of approximately n TCP SYNs.  On some systems n is silently limited.
              Default is 20.

       -E     no special environment.  Do not set up TCP-related environment variables.

       -v     verbose.  Print verbose messsages to standard output.

       -vv    more verbose.  Print more verbose messages to standard output.

SEE ALSO

       ipsvd(7), sslsvd(8), udpsvd(8), ipsvd-instruct(5), ipsvd-cdb(8), sslio(8)

       http://smarden.org/ipsvd/

AUTHOR

       Gerrit Pape <pape@smarden.org>

                                                                                                       tcpsvd(8)