accept

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



PROLOG
       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
       accept — accept a new connection on a socket

SYNOPSIS
       #include <sys/socket.h>

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

DESCRIPTION
       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 [EWOULDBLOCK].

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

RETURN VALUE
       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
       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.

EXAMPLES
       None.

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

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       bind(), connect(), listen(), socket()

       The Base Definitions volume of POSIX.1‐2008, <sys_socket.h>

COPYRIGHT
       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 .

       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                   2013                            ACCEPT(3P)