tcpserver(1) - phpMan
tcpserver(1) General Commands Manual tcpserver(1)
tcpserver - accepts incoming TCP connections.
tcpserver [ opts ] host port prog
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.
-q Quiet. Do not print error messages.
-Q (Default.) Print error messages.
-v Verbose. Print error messages and status messages.
-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.
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‐
-u uid Switch user ID to uid after preparing to receive connections. uid must be a posi‐
-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
-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.
-h (Default.) Look up the remote host name in DNS to set the environment variable
-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.
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.
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)