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)