NetBSD/share/man/man4/tcp.4

200 lines
5.9 KiB
Groff
Raw Normal View History

.\" $NetBSD: tcp.4,v 1.6 2000/05/22 02:01:34 itojun Exp $
.\"
.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
1993-03-21 12:45:37 +03:00
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)tcp.4 8.1 (Berkeley) 6/5/93
1993-03-21 12:45:37 +03:00
.\"
.Dd June 5, 1993
1993-03-21 12:45:37 +03:00
.Dt TCP 4
.Os
1993-03-21 12:45:37 +03:00
.Sh NAME
.Nm tcp
.Nd Internet Transmission Control Protocol
.Sh SYNOPSIS
.Fd #include <sys/socket.h>
.Fd #include <netinet/in.h>
.Ft int
.Fn socket AF_INET SOCK_STREAM 0
.Ft int
.Fn socket AF_INET6 SOCK_STREAM 0
1993-03-21 12:45:37 +03:00
.Sh DESCRIPTION
The
.Tn TCP
provides reliable, flow-controlled, two-way transmission of data.
It is a byte-stream protocol used to support the
1993-03-21 12:45:37 +03:00
.Dv SOCK_STREAM
abstraction.
.Tn TCP
uses the standard Internet address format and, in addition, provides
a per-host collection of
1993-03-21 12:45:37 +03:00
.Dq port addresses .
Thus, each address is composed of an Internet address specifying
the host and network, with a specific
1993-03-21 12:45:37 +03:00
.Tn TCP
port on the host identifying the peer entity.
.Pp
Sockets utilizing
.Tn TCP
are either
1993-03-21 12:45:37 +03:00
.Dq active
or
.Dq passive .
Active sockets initiate connections to passive
sockets.
By default
1993-03-21 12:45:37 +03:00
.Tn TCP
sockets are created active; to create a passive socket the
1993-03-21 12:45:37 +03:00
.Xr listen 2
system call must be used
after binding the socket with the
.Xr bind 2
system call.
Only passive sockets may use the
1993-03-21 12:45:37 +03:00
.Xr accept 2
call to accept incoming connections.
Only active sockets may use the
1993-03-21 12:45:37 +03:00
.Xr connect 2
call to initiate connections.
.Pp
Passive sockets may
.Dq underspecify
their location to match incoming connection requests from multiple networks.
This technique, termed
1993-03-21 12:45:37 +03:00
.Dq wildcard addressing ,
allows a single
server to provide service to clients on multiple networks.
To create a socket which listens on all networks, the Internet
address
.Dv INADDR_ANY
must be bound.
The
1993-03-21 12:45:37 +03:00
.Tn TCP
port may still be specified at this time; if the port is not
specified the system will assign one.
1993-03-21 12:45:37 +03:00
Once a connection has been established the socket's address is
fixed by the peer entity's location.
The address assigned the socket is the address associated with the
network interface through which packets are being transmitted and received.
Normally this address corresponds to the peer entity's network.
1993-03-21 12:45:37 +03:00
.Pp
.Tn TCP
supports one socket option which is set with
.Xr setsockopt 2
and tested with
.Xr getsockopt 2 .
Under most circumstances,
.Tn TCP
sends data when it is presented;
when outstanding data has not yet been acknowledged, it gathers
small amounts of output to be sent in a single packet once
an acknowledgement is received.
For a small number of clients, such as window systems
that send a stream of mouse events which receive no replies,
this packetization may cause significant delays.
Therefore,
.Tn TCP
provides a boolean option,
.Dv TCP_NODELAY
(from
.Aq Pa netinet/tcp.h ,
to defeat this algorithm.
The option level for the
.Xr setsockopt 2
1993-03-21 12:45:37 +03:00
call is the protocol number for
.Tn TCP ,
available from
.Xr getprotobyname 3 .
.Pp
Options at the
.Tn IP
network level may be used with
1993-03-21 12:45:37 +03:00
.Tn TCP ;
see
.Xr ip 4
or
.Xr ip6 4 .
1993-03-21 12:45:37 +03:00
Incoming connection requests that are source-routed are noted,
and the reverse source route is used in responding.
.Sh DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
.Bl -tag -width [EADDRNOTAVAIL]
.It Bq Er EISCONN
when trying to establish a connection on a socket which
already has one;
.It Bq Er ENOBUFS
when the system runs out of memory for
an internal data structure;
.It Bq Er ETIMEDOUT
when a connection was dropped
due to excessive retransmissions;
.It Bq Er ECONNRESET
when the remote peer
forces the connection to be closed;
.It Bq Er ECONNREFUSED
when the remote
peer actively refuses connection establishment (usually because
no process is listening to the port);
.It Bq Er EADDRINUSE
when an attempt
is made to create a socket with a port which has already been
allocated;
.It Bq Er EADDRNOTAVAIL
when an attempt is made to create a
1993-03-21 12:45:37 +03:00
socket with a network address for which no network interface
exists.
.El
.Sh SEE ALSO
.Xr getsockopt 2 ,
.Xr socket 2 ,
.Xr intro 4 ,
.Xr inet 4 ,
.Xr inet6 4 ,
.Xr ip 4 ,
.Xr ip6 4
.Rs
.%R RFC
.%N 793
.%D September 1981
.%T "Transmission Control Protocol"
.Re
.Rs
.%R RFC
.%N 1122
.%D October 1989
.%T "Requirements for Internet Hosts -- Communication Layers"
.Re
1993-03-21 12:45:37 +03:00
.Sh HISTORY
The
.Nm
protocol stack appeared in
.Bx 4.2 .