accept(2)                                                         accept(2)




 NAME
      accept - accept a connection on a socket

 SYNOPSIS
      #include <sys/socket.h>

    AF_CCITT only
      #include <x25/x25addrstr.h>

      int accept(int s, void *addr, int *addrlen);

    _XOPEN_SOURCE_EXTENDED only
      int accept(int s, struct sockaddr *addr, size_t *addrlen);

 DESCRIPTION
      The accept() system call is used with connection-based socket types,
      such as SOCK_STREAM.  The argument, s, is a socket descriptor created
      with socket(), bound to a local address by bind(), and listening for
      connections after a listen().  accept() extracts the first connection
      on the queue of pending connections, creates a new socket with the
      same properties as s, and returns a new file descriptor, ns, for the
      socket.

      If no pending connections are present on the queue and nonblocking
      mode has not been enabled with the fcntl() O_NONBLOCK or O_NDELAY
      flags or the ioctl() FIOSNBIO request, accept() blocks the caller
      until a connection is present.  O_NONBLOCK and O_NDELAY are defined in
      <sys/fcntl.h> (see fcntl(2) fcntl(5), and socket(7)).  FIOSNBIO and
      the equivalent request FIONBIO are defined in <sys/ioctl.h>, although
      use of FIONBIO is not recommended (see ioctl(2), ioctl(5), and
      socket(7)).

      If the socket has nonblocking mode enabled and no pending connections
      are present on the queue, accept() returns an error as described
      below.  The accepted socket, ns, cannot be used to accept more
      connections.  The original socket s remains open for incoming
      connection requests.  To determine whether a listening socket has
      pending connection requests ready for an accept() call, use select()
      for reading.

      The argument addr should point to a socket address structure.  The
      accept() call fills in this structure with the address of the
      connecting entity, as known to the underlying protocol.  In the case
      of AF_UNIX sockets, the peer's address is filled in only if the peer
      had done an explicit bind() before doing a connect().  Therefore, for
      AF_UNIX sockets, in the common case, when the peer had not done an
      explicit bind() before doing a connect(), the structure is filled with
      a string of nulls for the address.  The format of the address depends
      upon the protocol and the address-family of the socket s.  addrlen is
      a pointer to an int; it should initially contain the size of the
      structure pointed to by addr.  On return, it contains the actual



 Hewlett-Packard Company            - 1 -    HP-UX Release 10.20:  July 1996






 accept(2)                                                         accept(2)




      length (in bytes) of the address returned.  If the memory pointed to
      by addr is not large enough to contain the entire address, only the
      first addrlen bytes of the address are returned.  If addr is NULL or
      addrlen contains 0, then the connecting entity's address will not be
      returned.

      The fcntl() O_NONBLOCK and O_NDELAY flags and ioctl() FIOSNBIO request
      are all supported.  These features interact as follows:

         o  If the O_NONBLOCK or O_NDELAY flag has been set, accept()
            requests behave accordingly, regardless of any FIOSNBIO
            requests.

         o  If neither the O_NONBLOCK flag nor the O_NDELAY flag has been
            set, FIOSNBIO requests control the behavior of accept().

    AF_CCITT only
      The addr parameter to accept() returns addressing information for the
      connecting entity, except for the x25ifname[] field of addr which
      contains the name of the local X.25 interface through which the
      connection request arrived.  Call-acceptance can be controlled with
      the ioctl() X25_CALL_ACPT_APPROVAL request (see socketx25(7)).

 RETURN VALUE
      Upon successful completion, accept() returns a nonnegative integer
      which is a descriptor for the accepted socket.

      If an error occurs, accept() returns -1 and sets errno to indicate the
      cause.

 ERRORS
      If accept() fails, errno is set to one of the following values:

      [EAGAIN]            Nonblocking I/O is enabled using O_NONBLOCK and no
                          connections are present to be accepted.

      [EBADF]             The argument, s, is not a valid file descriptor.

      [EFAULT]            The addr parameter is not a valid pointer.

      [EINTR]             The call was interrupted by a signal before a
                          valid connection arrived.

      [EINVAL]            The socket referenced by s is not currently a
                          listen socket or has been shut down with
                          shutdown().  A listen() must be done before an
                          accept() is allowed.

      [EMFILE]            The maximum number of file descriptors for this
                          process are currently open.




 Hewlett-Packard Company            - 2 -    HP-UX Release 10.20:  July 1996






 accept(2)                                                         accept(2)




      [ENFILE]            The system's table of open files is full and no
                          more accept() calls can be processed at this time.

      [ENOBUFS]           No buffer space is available.  The accept() cannot
                          complete.  The queued socket connect request is
                          aborted.

      [ENOTSOCK]          The argument, s, is a valid file descriptor, but
                          it is not a socket.

      [EOPNOTSUPP]        The socket referenced by s does not suppport
                          accept().

      [EWOULDBLOCK]       Nonblocking I/O is enabled using O_NDELAY or
                          FIOSNBIO and no connections are present to be
                          accepted.

 AUTHOR
      accept() was developed by the University of California, Berkeley.

 FUTURE DIRECTION
      The default behavior in this release is still the classic HP-UX BSD
      Sockets, however it will be changed to X/Open Sockets in some future
      release.  At that time, any HP-UX BSD Sockets behavior which is
      incompatible with X/Open Sockets may be obsoleted.  HP customers are
      advised to migrate their applications to conform to X/Open
      specification( see xopen_networking(7) ).

 SEE ALSO
      bind(2), connect(2), listen(2), select(2), socket(2) socketx25(7),
      xopen_networking(7).

 STANDARDS CONFORMANCE
      accept(): XPG4




















 Hewlett-Packard Company            - 3 -    HP-UX Release 10.20:  July 1996