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
              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 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 {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, 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
       Standard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .