1ACCEPT(3P) POSIX Programmer's Manual ACCEPT(3P)
2
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.
10
12 accept — accept a new connection on a socket
13
15 #include <sys/socket.h>
16 int accept(int socket, struct sockaddr *restrict address,
18 socklen_t *restrict address_len);
19
21 The accept() function shall extract the first connection on the queue
22 of pending connections, create a new socket with the same socket type
23 protocol and address family as the specified socket, and allocate a new
24 file descriptor for that socket. The file descriptor shall be allocated
25 as described in Section 2.14, File Descriptor Allocation.
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,
66 errno shall be set to indicate the error, and any object pointed to by
67 address_len shall remain unchanged.
68
70 The accept() function shall fail if:
71 EAGAIN or EWOULDBLOCK
73 O_NONBLOCK is set for the socket file descriptor and no connec‐
74 tions are present to be accepted.
75 EBADF The socket argument is not a valid file descriptor.
77 ECONNABORTED
79 A connection has been aborted.
80 EINTR The accept() function was interrupted by a signal that was
82 caught before a valid connection arrived.
83 EINVAL The socket is not accepting connections.
85 EMFILE All file descriptors available to the process are currently
87 open.
88 ENFILE The maximum number of file descriptors in the system are already
90 open.
91 ENOBUFS
93 No buffer space is available.
94 ENOMEM There was insufficient memory available to complete the opera‐
96 tion.
97 ENOTSOCK
99 The socket argument does not refer to a socket.
100 EOPNOTSUPP
102 The socket type of the specified socket does not support accept‐
103 ing connections.
104 The accept() function may fail if:
106 EPROTO A protocol error has occurred; for example, the STREAMS protocol
108 stack has not been initialized.
109 The following sections are informative.
111
113 None.
114
116 When a connection is available, select() indicates that the file
117 descriptor for the socket is ready for reading.
118
120 None.
121
123 None.
124
126 Section 2.14, File Descriptor Allocation, bind(), connect(), listen(),
127 socket()
128 The Base Definitions volume of POSIX.1‐2017, <sys_socket.h>
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132 Portions of this text are reprinted and reproduced in electronic form
133 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
134 table Operating System Interface (POSIX), The Open Group Base Specifi‐
135 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
136 Electrical and Electronics Engineers, Inc and The Open Group. In the
137 event of any discrepancy between this version and the original IEEE and
138 The Open Group Standard, the original IEEE and The Open Group Standard
139 is the referee document. The original Standard can be obtained online
140 at http://www.opengroup.org/unix/online.html .
141 Any typographical or formatting errors that appear in this page are
143 most likely to have been introduced during the conversion of the source
144 files to man page format. To report such errors, see https://www.ker‐
145 nel.org/doc/man-pages/reporting_bugs.html .
146IEEE/The Open Group 2017 ACCEPT(3P)