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accept(3posix)


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.12008, <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 .



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