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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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ACCEPT(3P) POSIX Programmer's Manual ACCEPT(3P)
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
#include <sys/socket.h>
int accept(int socket, struct sockaddr *restrict address,
socklen_t *restrict address_len);
The accept() 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. The file
descriptor shall be allocated as described in Section 2.14, File
Descriptor Allocation.
The accept() function takes the following arguments:
socket Specifies a socket that was created with socket(),
has been bound to an address with bind(), and has
issued a successful call to listen().
address Either a null pointer, or a pointer to a sockaddr
structure where the address of the connecting socket
shall be returned.
address_len 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.
If address is not a null pointer, the address of the peer for the
accepted connection shall be stored in the sockaddr structure
pointed 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 sockaddr 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 is unspecified.
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, accept() shall fail
and set errno to [EAGAIN] or [EWOULDBLOCK].
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, errno shall be set to indicate the error, and
any object pointed to by address_len shall remain unchanged.
The accept() function shall fail if:
EAGAIN or EWOULDBLOCK
O_NONBLOCK is set for the socket file descriptor and no
connections are present to be accepted.
EBADF The socket argument is not a valid file descriptor.
ECONNABORTED
A connection has been aborted.
EINTR The accept() function was interrupted by a signal that was
caught before a valid connection arrived.
EINVAL The socket is not accepting connections.
EMFILE All file descriptors available to the process are
currently open.
ENFILE The maximum number of file descriptors in the system are
already open.
ENOBUFS
No buffer space is available.
ENOMEM There was insufficient memory available to complete the
operation.
ENOTSOCK
The socket argument does not refer to a socket.
EOPNOTSUPP
The socket type of the specified socket does not support
accepting connections.
The accept() function may fail if:
EPROTO A protocol error has occurred; for example, the STREAMS
protocol stack has not been initialized.
The following sections are informative.
None.
When a connection is available, select() indicates that the file
descriptor for the socket is ready for reading.
None.
None.
Section 2.14, File Descriptor Allocation, bind(3p), connect(3p),
listen(3p), socket(3p)
The Base Definitions volume of POSIX.1‐2017, sys_socket.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 ACCEPT(3P)
Pages that refer to this page: sys_socket.h(0p), connect(3p), getpeername(3p), getsockname(3p), listen(3p), pselect(3p), socket(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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