1 .\" Copyright (c) 1983, 1990, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 4. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)accept.2 8.2 (Berkeley) 12/11/93
36 .Nd accept a connection on a socket
43 .Fn accept "int s" "struct sockaddr * restrict addr" "socklen_t * restrict addrlen"
47 is a socket that has been created with
49 bound to an address with
51 and is listening for connections after a
55 system call extracts the first connection request on the
56 queue of pending connections, creates a new socket,
57 and allocates a new file descriptor for the socket which
58 inherits the state of the
62 properties and the destination of
66 signals from the original socket
69 If no pending connections are
70 present on the queue, and the original socket
71 is not marked as non-blocking,
73 blocks the caller until a connection is present.
74 If the original socket
75 is marked non-blocking and no pending
76 connections are present on the queue,
78 returns an error as described below.
81 to accept more connections.
88 is a result argument that is filled-in with
89 the address of the connecting entity,
90 as known to the communications layer.
91 The exact format of the
93 argument is determined by the domain in which the communication
95 A null pointer may be specified for
97 if the address information is not desired;
100 is not used and should also be null.
104 is a value-result argument; it should initially contain the
105 amount of space pointed to by
107 on return it will contain the actual length (in bytes) of the
110 is used with connection-based socket types, currently with
115 a socket for the purposes of doing an
117 by selecting it for read.
119 For certain protocols which require an explicit confirmation,
126 as merely dequeueing the next connection
127 request and not implying confirmation.
128 Confirmation can be implied by a normal read or write on the new
129 file descriptor, and rejection can be implied by closing the
132 For some applications, performance may be enhanced by using an
134 to pre-process incoming connections.
136 Portable programs should not rely on the
140 properties and the signal destination being inherited,
141 but should set them explicitly using
144 The call returns \-1 on error.
145 If it succeeds, it returns a non-negative
146 integer that is a descriptor for the accepted socket.
150 system call will fail if:
153 The descriptor is invalid.
157 operation was interrupted.
159 The per-process descriptor table is full.
161 The system file table is full.
163 The descriptor references a file, not a socket.
166 has not been called on the socket descriptor.
170 argument is negative.
174 argument is not in a writable part of the
176 .It Bq Er EWOULDBLOCK
177 The socket is marked non-blocking and no connections
178 are present to be accepted.
179 .It Bq Er ECONNABORTED
180 A connection arrived, but it was closed while waiting
195 system call appeared in