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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  success-
                   ful 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  con-
       nection  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 connec-
              tions 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 opera-
              tion.
       ENOTSOCK
              The socket argument does not refer to a socket.
       EOPNOTSUPP
              The socket type of the specified socket does not support accept-
              ing 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 Electri-
       cal  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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           ACCEPT(3P)