.TH tcpsvd 8
.SH NAME
tcpsvd \- TCP/IP service daemon
.SH SYNOPSIS
.B tcpsvd
[\-hpEvv] [\-c
.I n\fR] [\-C
.I n\fR:\fImsg\fR] [\-b
.I n\fR] [\-u
.I user\fR] [\-l
.I name\fR] [\-i
.IR dir |\-x
.IR cdb ]
[ \-t
.IR sec ]
.I host
.I port
.I prog
.SH DESCRIPTION
.B tcpsvd
creates a TCP/IP socket, binds it to the address
.IR host :\fIport\fR,
and listens on the socket for incoming connections.
.P
On each incoming connection,
.B tcpsvd
conditionally runs a program, with standard input reading from the socket,
and standard output writing to the socket, to handle this connection.
.B tcpsvd
keeps listening on the socket for new connections, and can handle multiple
connections simultaneously.
.P
.B tcpsvd
optionally checks for special instructions depending on the IP address or
hostname of the client that initiated the connection, see
.BR ipsvd-instruct (5).
.SH OPTIONS
.TP
.I host
.I host
either is a hostname, or a dotted-decimal IP address, or 0.
If
.I host
is 0,
.B tcpsvd
accepts connections to any local IP address.
.TP
.I port
.B tcpsvd
accepts connections to
.IR host :\fIport\fR.
.I port
may be a name from /etc/services or a number.
.TP
.I prog
.I prog
consists of one or more arguments.
For each connection,
.B tcpsvd
normally runs
.IR 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
.BR tcp-environ (5)
.TP
.B \-i \fIdir
read instructions for handling new connections from the instructions
directory
.IR dir .
See
.BR ipsvd-instruct (5)
for details.
.TP
.B \-x \fIcdb
read instructions for handling new connections from the constant database
.IR cdb .
The constant database normally is created from an instructions directory by
running
.BR ipsvd-cdb (8).
.TP
.B \-t \fIsec
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
.I sec
seconds;
.B 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.
.TP
.B \-l \fIname
local hostname.
Do not look up the local hostname in DNS, but use
.I name
as hostname.
This option must be set if
.B tcpsvd
listens on port 53 to avoid loops.
.TP
.B \-u \fI[:]user[:group]
drop permissions.
Set uid and gid to the
.IR user 's
uid and gid, as found in
.IR /etc/passwd ,
before running
.IR prog .
If
.I user
is followed by a colon and a
.IR group ,
set the gid to
.IR group 's
gid, as found in
.IR /etc/group ,
instead of
.IR user 's
gid.
If
.I group
consists of a colon-separated list of group names,
set the group ids of all listed groups.
If
.I user
is prefixed with a colon, the
.I user
and all
.I group
arguments are interpreted as uid and gids respectively, and not looked up in
the password or group file.
All supplementary groups are removed.
.TP
.B \-c \fIn
concurrency.
Handle up to
.I n
connections simultaneously.
Default is 30.
If there are
.I n
connections active,
.B tcpsvd
defers acceptance of a new connection until an active connection is closed.
.TP
.B \-C \fIn\fR[:\fImsg\fR]
per host concurrency.
Allow only up to
.I n
connections from the same IP address simultaneously.
If there are
.I n
active connections from one IP address, new incoming connections from this IP
address are closed immediately.
If
.I n
is followed by
.RI : msg\fR,
the message
.I msg
is written to the client if possible, before closing the connection.
By default
.I msg
is empty.
See
.BR ipsvd-instruct (5)
for supported escape sequences in
.IR msg .

For each accepted connection, the current per host concurrency is available
through the environment variable
.IR TCPCONCURRENCY .
.I n
and
.I msg
can be overwritten by
.BR ipsvd (7)
instructions, see
.BR ipsvd-instruct (5). 
By default
.B tcpsvd
doesn't keep track of connections.
.TP
.B \-h
Look up the client's hostname in DNS.
.TP
.B \-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.
.TP
.B \-b \fIn
backlog.
Allow a backlog of approximately
.I n
TCP SYNs.
On some systems
.I n
is silently limited.
Default is 20.
.TP
.B \-E
no special environment.
Do not set up TCP-related environment variables.
.TP
.B \-v
verbose.
Print verbose messsages to standard output.
.TP
.B \-vv
more verbose.
Print more verbose messages to standard output.
.SH SEE ALSO
ipsvd(7),
sslsvd(8),
udpsvd(8),
ipsvd-instruct(5),
ipsvd-cdb(8),
sslio(8)
.P
http://smarden.org/ipsvd/
.SH AUTHOR
Gerrit Pape <pape@smarden.org>