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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"
45 .Fn accept4 "int s" "struct sockaddr * restrict addr" "socklen_t * restrict addrlen" "int flags"
49 is a socket that has been created with
51 bound to an address with
53 and is listening for connections after a
57 system call extracts the first connection request on the
58 queue of pending connections, creates a new socket,
59 and allocates a new file descriptor for the socket which
60 inherits the state of the
64 properties and the destination of
68 signals from the original socket
73 system call is similar,
76 property of the new socket is instead determined by the
84 the signal destination is cleared
85 and the close-on-exec flag on the new file descriptor can be set via the
91 If no pending connections are
92 present on the queue, and the original socket
93 is not marked as non-blocking,
95 blocks the caller until a connection is present.
96 If the original socket
97 is marked non-blocking and no pending
98 connections are present on the queue,
100 returns an error as described below.
103 to accept more connections.
110 is a result argument that is filled-in with
111 the address of the connecting entity,
112 as known to the communications layer.
113 The exact format of the
115 argument is determined by the domain in which the communication
117 A null pointer may be specified for
119 if the address information is not desired;
122 is not used and should also be null.
126 is a value-result argument; it should initially contain the
127 amount of space pointed to by
129 on return it will contain the actual length (in bytes) of the
132 is used with connection-based socket types, currently with
137 a socket for the purposes of doing an
139 by selecting it for read.
141 For certain protocols which require an explicit confirmation,
148 as merely dequeueing the next connection
149 request and not implying confirmation.
150 Confirmation can be implied by a normal read or write on the new
151 file descriptor, and rejection can be implied by closing the
154 For some applications, performance may be enhanced by using an
156 to pre-process incoming connections.
160 portable programs should not rely on the
164 properties and the signal destination being inherited,
165 but should set them explicitly using
168 sets these properties consistently,
169 but may not be fully portable across
173 These calls return \-1 on error.
174 If they succeed, they return a non-negative
175 integer that is a descriptor for the accepted socket.
181 system calls will fail if:
184 The descriptor is invalid.
188 operation was interrupted.
190 The per-process descriptor table is full.
192 The system file table is full.
194 The descriptor references a file, not a socket.
197 has not been called on the socket descriptor.
201 argument is not in a writable part of the
203 .It Bq Er EWOULDBLOCK
204 The socket is marked non-blocking and no connections
205 are present to be accepted.
206 .It Bq Er ECONNABORTED
207 A connection arrived, but it was closed while waiting
213 system call will also fail if:
232 system call appeared in
237 system call appeared in