1ACCEPT(3P) POSIX Programmer's Manual ACCEPT(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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13 accept — accept a new connection on a socket
14
16 #include <sys/socket.h>
17 int accept(int socket, struct sockaddr *restrict address,
19 socklen_t *restrict address_len);
20
22 The accept() function shall extract the first connection on the queue
23 of pending connections, create a new socket with the same socket type
24 protocol and address family as the specified socket, and allocate a new
25 file descriptor for that socket.
26 The accept() function takes the following arguments:
28 socket Specifies a socket that was created with socket(), has been
30 bound to an address with bind(), and has issued a success‐
31 ful call to listen().
32 address Either a null pointer, or a pointer to a sockaddr structure
34 where the address of the connecting socket shall be
35 returned.
36 address_len Either a null pointer, if address is a null pointer, or a
38 pointer to a socklen_t object which on input specifies the
39 length of the supplied sockaddr structure, and on output
40 specifies the length of the stored address.
41 If address is not a null pointer, the address of the peer for the
43 accepted connection shall be stored in the sockaddr structure pointed
44 to by address, and the length of this address shall be stored in the
45 object pointed to by address_len.
46 If the actual length of the address is greater than the length of the
48 supplied sockaddr structure, the stored address shall be truncated.
49 If the protocol permits connections by unbound clients, and the peer is
51 not bound, then the value stored in the object pointed to by address is
52 unspecified.
53 If the listen queue is empty of connection requests and O_NONBLOCK is
55 not set on the file descriptor for the socket, accept() shall block
56 until a connection is present. If the listen() queue is empty of con‐
57 nection requests and O_NONBLOCK is set on the file descriptor for the
58 socket, accept() shall fail and set errno to [EAGAIN] or [EWOULDBLOCK].
59 The accepted socket cannot itself accept more connections. The original
61 socket remains open and can accept more connections.
62
64 Upon successful completion, accept() shall return the non-negative file
65 descriptor of the accepted socket. Otherwise, −1 shall be returned and
66 errno set to indicate the error.
67
69 The accept() function shall fail if:
70 EAGAIN or EWOULDBLOCK
72 O_NONBLOCK is set for the socket file descriptor and no connec‐
73 tions are present to be accepted.
74 EBADF The socket argument is not a valid file descriptor.
76 ECONNABORTED
78 A connection has been aborted.
79 EINTR The accept() function was interrupted by a signal that was
81 caught before a valid connection arrived.
82 EINVAL The socket is not accepting connections.
84 EMFILE All file descriptors available to the process are currently
86 open.
87 ENFILE The maximum number of file descriptors in the system are already
89 open.
90 ENOBUFS
92 No buffer space is available.
93 ENOMEM There was insufficient memory available to complete the opera‐
95 tion.
96 ENOTSOCK
98 The socket argument does not refer to a socket.
99 EOPNOTSUPP
101 The socket type of the specified socket does not support accept‐
102 ing connections.
103 The accept() function may fail if:
105 EPROTO A protocol error has occurred; for example, the STREAMS protocol
107 stack has not been initialized.
108 The following sections are informative.
110
112 None.
113
115 When a connection is available, select() indicates that the file
116 descriptor for the socket is ready for reading.
117
119 None.
120
122 None.
123
125 bind(), connect(), listen(), socket()
126 The Base Definitions volume of POSIX.1‐2008, <sys_socket.h>
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130 Portions of this text are reprinted and reproduced in electronic form
131 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
132 -- Portable Operating System Interface (POSIX), The Open Group Base
133 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
134 cal and Electronics Engineers, Inc and The Open Group. (This is
135 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
136 event of any discrepancy between this version and the original IEEE and
137 The Open Group Standard, the original IEEE and The Open Group Standard
138 is the referee document. The original Standard can be obtained online
139 at http://www.unix.org/online.html .
140 Any typographical or formatting errors that appear in this page are
142 most likely to have been introduced during the conversion of the source
143 files to man page format. To report such errors, see https://www.ker‐
144 nel.org/doc/man-pages/reporting_bugs.html .
145IEEE/The Open Group 2013 ACCEPT(3P)