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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"
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
60 property from the original socket
63 If no pending connections are
64 present on the queue, and the original socket
65 is not marked as non-blocking,
67 blocks the caller until a connection is present.
68 If the original socket
69 is marked non-blocking and no pending
70 connections are present on the queue,
72 returns an error as described below.
75 to accept more connections.
82 is a result argument that is filled-in with
83 the address of the connecting entity,
84 as known to the communications layer.
85 The exact format of the
87 argument is determined by the domain in which the communication
89 A null pointer may be specified for
91 if the address information is not desired;
94 is not used and should also be null.
98 is a value-result argument; it should initially contain the
99 amount of space pointed to by
101 on return it will contain the actual length (in bytes) of the
104 is used with connection-based socket types, currently with
109 a socket for the purposes of doing an
111 by selecting it for read.
113 For certain protocols which require an explicit confirmation,
120 as merely dequeueing the next connection
121 request and not implying confirmation.
122 Confirmation can be implied by a normal read or write on the new
123 file descriptor, and rejection can be implied by closing the
126 For some applications, performance may be enhanced by using an
128 to pre-process incoming connections.
130 The call returns \-1 on error.
131 If it succeeds, it returns a non-negative
132 integer that is a descriptor for the accepted socket.
136 system call will fail if:
139 The descriptor is invalid.
143 operation was interrupted.
145 The per-process descriptor table is full.
147 The system file table is full.
149 The descriptor references a file, not a socket.
152 has not been called on the socket descriptor.
156 argument is negative.
160 argument is not in a writable part of the
162 .It Bq Er EWOULDBLOCK
163 The socket is marked non-blocking and no connections
164 are present to be accepted.
165 .It Bq Er ECONNABORTED
166 A connection arrived, but it was closed while waiting
181 system call appeared in