accept(3p) — Linux manual page


ACCEPT(3P)                POSIX Programmer's Manual               ACCEPT(3P)

PROLOG         top

       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.

NAME         top

       accept — accept a new connection on a socket

SYNOPSIS         top

       #include <sys/socket.h>

       int accept(int socket, struct sockaddr *restrict address,
           socklen_t *restrict address_len);

DESCRIPTION         top

       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 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

       The accepted socket cannot itself accept more connections. The
       original socket remains open and can accept more connections.

RETURN VALUE         top

       Upon successful completion, accept() shall return the non-negative
       file descriptor of the accepted socket.  Otherwise, −1 shall be
       returned and errno set to indicate the error.

ERRORS         top

       The accept() function shall fail if:

              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.

              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

       ENFILE The maximum number of file descriptors in the system are
              already open.

              No buffer space is available.

       ENOMEM 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
              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.

EXAMPLES         top



       When a connection is available, select() indicates that the file
       descriptor for the socket is ready for reading.

RATIONALE         top




SEE ALSO         top

       bind(3p), connect(3p), listen(3p), socket(3p)

       The Base Definitions volume of POSIX.1‐2008, sys_socket.h(0p)

COPYRIGHT         top

       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 .

       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 .

IEEE/The Open Group                 2013                          ACCEPT(3P)

Pages that refer to this page: sys_socket.h(0p)connect(3p)getpeername(3p)getsockname(3p)listen(3p)pselect(3p)socket(3p)