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 .