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28 .\" @(#)accept.2 8.2 (Berkeley) 12/11/93
29 .\" $FreeBSD: src/lib/libc/sys/accept.2,v 1.10.2.11 2002/05/09 02:24:40 silby Exp $
30 .\" $DragonFly: src/lib/libc/sys/accept.2,v 1.4 2006/06/25 10:55:51 corecode Exp $
37 .Nd accept a connection on a socket
44 .Fn accept "int s" "struct sockaddr *addr" "socklen_t *addrlen"
48 is a socket that has been created with
50 bound to an address with
52 and is listening for connections after a
57 extracts the first connection request
58 on the queue of pending connections, creates
59 a new socket with the same properties as
61 and allocates a new file descriptor
62 for the socket. If no pending connections are
63 present on the queue, and the socket is not marked
66 blocks the caller until a connection is present.
67 If the socket is marked non-blocking and no pending
68 connections are present on the queue,
70 returns an error as described below.
73 to accept more connections. The original socket
79 is a result parameter that is filled-in with
80 the address of the connecting entity,
81 as known to the communications layer.
82 The exact format of the
84 parameter is determined by the domain in which the communication
86 To ensure that the returned address fits,
88 should have a size of at least
89 .Ft sizeof(struct sockaddr_storage) .
92 is a value-result parameter; it should initially contain the
93 amount of space pointed to by
95 on return it will contain the actual length (in bytes) of the
98 is used with connection-based socket types, currently with
103 a socket for the purposes of doing an
105 by selecting it for read.
107 For certain protocols which require an explicit confirmation,
114 as merely dequeueing the next connection
115 request and not implying confirmation.
116 Confirmation can be implied by a normal read or write on the new
117 file descriptor, and rejection can be implied by closing the
120 For some applications, performance may be enhanced by using an
122 to pre-process incoming connections.
124 The call returns \-1 on error. If it succeeds, it returns a non-negative
125 integer that is a descriptor for the accepted socket.
132 The descriptor is invalid.
136 operation was interrupted.
138 The per-process descriptor table is full.
140 The system file table is full.
142 The descriptor references a file, not a socket.
145 has not been called on the socket descriptor.
149 parameter is not in a writable part of the
151 .It Bq Er EWOULDBLOCK
152 The socket is marked non-blocking and no connections
153 are present to be accepted.
154 .It Bq Er ECONNABORTED
155 A connection arrived, but it was closed while waiting