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 (con-
       sult 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 suc-
              cessful 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
              Points  to  a  socklen_t  structure 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 connec-
       tions.

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 {OPEN_MAX} file descriptors are currently open in the calling process.

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

       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:

       ENOBUFS
              No buffer space is available.

       ENOMEM There was insufficient memory available to complete the operation.

       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 IEEE Std 1003.1-2001, <sys/socket.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    ACCEPT(3P)