This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding Linux
manual page for details of Linux behavior), or the interface may not be
implemented on Linux.
accept — accept a new connection on a socket
int accept(int socket, struct sockaddr *restrict address,
socklen_t *restrict address_len);
() function shall extract the first connection on the queue of
pending connections, create a new socket with the same socket type protocol
and address family as the specified socket, and allocate a new file descriptor
for that socket.
() function takes the following arguments:
- Specifies a socket that was created with socket(),
has been bound to an address with bind(), and has issued a
successful call to listen().
- Either a null pointer, or a pointer to a sockaddr
structure where the address of the connecting socket shall be
- Either a null pointer, if address is a null pointer,
or a pointer to a socklen_t object which on input specifies the
length of the supplied sockaddr structure, and on output specifies
the length of the stored address.
is not a null pointer, the address of the peer for the
accepted connection shall be stored in the sockaddr
to by address
, and the length of this address shall be stored in the
object pointed to by address_len
If the actual length of the address is greater than the length of the supplied
structure, the stored address shall be truncated.
If the protocol permits connections by unbound clients, and the peer is not
bound, then the value stored in the object pointed to by address
If the listen queue is empty of connection requests and O_NONBLOCK is not set on
the file descriptor for the socket, accept
() shall block until a
connection is present. If the listen
() queue is empty of connection
requests and O_NONBLOCK is set on the file descriptor for the socket,
() shall fail and set errno
The accepted socket cannot itself accept more connections. The original socket
remains open and can accept more connections.
Upon successful completion, accept
() shall return the non-negative file
descriptor of the accepted socket. Otherwise, −1 shall be returned and
set to indicate the error.
() function shall fail if:
- EAGAIN or EWOULDBLOCK
O_NONBLOCK is set for the socket file descriptor and no connections are
present to be accepted.
- The socket argument is not a valid file
A connection has been aborted.
- The accept() function was interrupted by a signal
that was caught before a valid connection arrived.
- The socket is not accepting connections.
- All file descriptors available to the process are currently
- The maximum number of file descriptors in the system are
- No buffer space is available.
- There was insufficient memory available to complete the
- The socket argument does not refer to a socket.
- The socket type of the specified socket does not support
() function may fail if:
The following sections are informative.
- A protocol error has occurred; for example, the STREAMS
protocol stack has not been initialized.
When a connection is available, select
() indicates that the file
descriptor for the socket is ready for reading.
The Base Definitions volume of POSIX.1‐2008,
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
7, Copyright (C) 2013 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013
Technical Corrigendum 1 applied.) In the event of any discrepancy between this
version and the original IEEE and The Open Group Standard, the original IEEE
and The Open Group Standard is the referee document. The original Standard can
be obtained online at http://www.unix.org/online.html .
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