NAME

       tcpserver - accept incoming TCP connections


SYNOPSIS

       tcpserver [ -146jpPhHrRoOdDqQv ] [ -climit ] [ -X-xrules.cdb ] [
       -Bbanner ] [ -ggid ] [ -uuid ] [ -bbacklog ] [ -llocalname ] [
       -ttimeout ] [ -Iifname ] 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.



BINDINGS

       tcpserver will attach to the primary IP address of host while the host
       name is fed through qualification using dns_ip6_qualify.  If host is
       given as dotted decimal IPv4 or compactified IPv6 address, tcpserver
       will bind uniquely to those.  In order to bind tcpserver to a LLU IPv6
       address (ie. fe80::a:b:c) additionally the interface name -Iifname has
       to be provided.

       Note: The kernel might use temporary changing SLAAC addresses.

       tcpserver can be instructed to be multi-homing capable while binding to
       all available IP addresses. Now host is given as '0' or '::' perhaps
       accompanied by the flags -4 or -6.

       Further, tcpserver may be forced to provide dual-stack capabilities,
       thus allowing IPv4 and IPv6 clients to attach to the same instance once
       host equals ':0' as pseudo IP address.

       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

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

       -4     Use IPv4 sockets.

       -6     Force IPv6 mode. This will set PROTO to TCP6 and put IPv4-mapped
              IPv6 addresses in TCPLOCALIP and TCPREMOTEIP.

       -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.


              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.

       -Iifname
              Bind to the network interface ifname ("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 IPv4/IPv6
              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
       addresses:

              127./8

              ::1/128

       this is the host-scoped loopback-address, while

              fe80::1%lo0

       is the link-scoped looback-address and lo0 is the name of the loopback
       interface.


DNS RESOLVER SETTINGS

       Use $DNSCACHEIP to set the DNS resolver's IP(s) dynamically
       irrespectively from the settings in /etc/resolv.conf.  The individual
       IPs are separated by blanks; IPv6 LLU addresses may be appended with
       the interface name following a '%' sign.  If the environment variable
       $LOCALDOMAIN is populated, this name will be appended to unqualified
       host names.  Additional rewriting of local to public names is
       facilitated in case the file /etc/dnsrewritefile exists and is
       populated, or alternatively, the environment variable $DNSREWRITEFILE
       points to a different file.


ENVIRONMENT VARIABLES SET

       tcpserver provides the following environment variables:

       PROTO this is either TCP or TCP6.

       The interface name for IPv6 connections: TCP6INTERFACE.

       The local information: TCPLOCALIP, TCP6LOCLAIP, TCPLOCALPORT,
       TCP6LOCALPORT, TCPLOCALHOST, TCP6LOCALHOST.

       The IP address of connection: TCPREMOTEIP and TCP6REMOTEIP.

       The remote port number: TCPREMOTEPORT, TCP6REMOTEPORT.

       The hostname (FQDN) of the peer, if available: TCPREMOTEHOST,
       TCP6REMOTEHOST.

       In case of a successfull IDENT lookup: TCPREMOTEINFO.


LOGGING

       Invoking tcpserver with the option -v will provide a logging of the
       session including local and remote IP addresses and port.  In case the
       option -h is given, the remote hostname is displayed, if available.


SEE ALSO

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


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