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 socket(7)							   socket(7)




 NAME
      socket - interprocess communications

 DESCRIPTION
      Sockets are communication endpoints that allow processes to
      communicate either locally or remotely.  They are accessed by means of
      a set of system calls (see socket(2)).

      The following ioctl() requests are defined in <sys/ioctl.h> (see
      ioctl(2)):

      FIOSNBIO	     If the int with the address arg is non-zero, the socket
		     is put into non-blocking mode.  Otherwise, the socket
		     is put into blocking mode.	 Blocking mode is the
		     default.  The FIONBIO request is equivalent to the
		     FIOSNBIO request, although using FIONBIO is not
		     recommended.  See accept(2), connect(2), recv(2), and
		     send(2) for an explanation of how non-blocking mode is
		     used.

      FIONREAD	     For SOCK_STREAM sockets, the number of bytes currently
		     readable from this socket is returned in the integer
		     with the address arg.  For SOCK_DGRAM sockets, the
		     number of bytes currently readable, plus the size of
		     the sockaddr structure (defined in <sys/socket.h>), is
		     returned in the integer with the address arg.

      SIOCATMARK     For SOCK_STREAM TCP sockets, on return the integer with
		     the address arg is non-zero if the inbound TCP stream
		     has been read up to where the out-of-band data byte
		     starts.  Otherwise, the inbound TCP stream has not yet
		     been read up to where the out-of-band data byte starts.
		     For sockets other than SOCK_STREAM TCP sockets, on
		     return the integer with the address arg is always zero.

      SIOCSPGRP	     This request sets the process group or process ID
		     associated with the socket to be the value of the
		     integer with the address arg.  A process group or
		     process ID associated with the socket in this manner is
		     signaled when the state of the socket changes: SIGURG
		     is delivered upon the receipt of out-of-band data;
		     SIGIO is delivered if the socket is asynchronous, as
		     described in FIOASYNC below.  If the value of the
		     integer with the address arg is positive, the signal is
		     sent to the process whose process ID matches the value
		     specified.	 If the value is negative, the signal is
		     sent to all the processes that have a process group
		     equal to the absolute value of the value specified.  If
		     the value is zero, no signal is sent to any process.
		     It is necessary to issue this request with a non-zero
		     integer value to enable the signal delivery mechanism



 Hewlett-Packard Company	    - 1 -   HP-UX Release 11i: November 2000






 socket(7)							   socket(7)




		     described above.  The default for the process group or
		     process ID value is zero.

      SIOCGPGRP	     This request returns the process group or process ID
		     associated with the socket in the integer with the
		     address arg.  See the explanation for SIOCSPGRP above
		     for more details on the meaning of the integer value
		     returned.

      FIOASYNC	     If the integer whose address is arg is non-zero, this
		     request sets the state of the socket as asynchronous.
		     Otherwise, the socket is put into synchronous mode (the
		     default).	Asynchronous mode enables the delivery of
		     the SIGIO signal when either of the following
		     conditions is met.

			  +  New data arrives.

			  +  For connection-oriented protocols, whenever
			     additional outgoing buffer space becomes
			     available or the connection is established or
			     broken.

		     The process group or process ID associated with the
		     socket must be non-zero in order for SIGIO signals to
		     be sent. The signal is delivered according to the
		     semantics of SIOCSPGRP described above.

      The fcntl(2) O_NDELAY and O_NONBLOCK flags (defined in <fcntl.h>) are
      supported by sockets.  If the O_NONBLOCK flag is set, the socket is
      put into POSIX-style non-blocking mode.  If the O_NDELAY flag is set,
      the socket is put into non-blocking mode.	 Otherwise, the socket is
      put into blocking mode.  Blocking mode is the default.  See accept(2),
      connect(2), recv(2), and send(2) for an explanation of how these forms
      of non-blocking mode are used.

      Since the fcntl() O_NONBLOCK and O_NDELAY flags and ioctl() FIOSNBIO
      requests are supported, the following clarifies on how these features
      interact.	 If the O_NONBLOCK or O_NDELAY flag has been set, recv() and
      send() requests behave accordingly, regardless of any FIOSNBIO
      requests.	 If neither the O_NONBLOCK flag nor the O_NDELAY flag has
      been set, FIOSNBIO requests control the the behavior of recv() and
      send().

 DEPENDENCIES
    AF_CCITT Only
      Only the FIOSNBIO, FIONREAD, SIOCGPGRP, and SIOCSPGRP ioctl() requests
      are defined for af_ccitt sockets.

 AUTHOR
      socket was developed by the University of California, Berkeley.



 Hewlett-Packard Company	    - 2 -   HP-UX Release 11i: November 2000






 socket(7)							   socket(7)




 SEE ALSO
      fcntl(2), getsockopt(2), ioctl(2), socket(2).




















































 Hewlett-Packard Company	    - 3 -   HP-UX Release 11i: November 2000