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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 dif-
       fer (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 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().

              Either a null pointer, or a pointer to a sockaddr structure where the address of the  connecting  socket
              shall be returned.

              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

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

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

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

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

              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:

              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.


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



       bind(), connect(), listen(), socket(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/socket.h>

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions Issue 6, Copyright (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 Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at .

IEEE/The Open Group                  2003                           ACCEPT(3P)