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 UNIX(7P)							    UNIX(7P)




 NAME
      UNIX - local communication domain protocol

 SYNOPSIS
      #include <&lt&lt&lt;sys/types.h>&gt&gt&gt;
      #include <&lt&lt&lt;sys/un.h>&gt&gt&gt;

 DESCRIPTION
      The local communication domain protocol, commonly referred to in the
      industry as the Unix domain protocol, utilizes the path name address
      format and the AF_UNIX address family.  This protocol can be used as
      an alternative to the Internet protocol family (TCP/IP or UDP/IP) for
      communication between processes executing on the same node.  It has a
      significant throughput advantage when compared with local IP loopback,
      due primarily to its much lower code execution overhead.	Data is
      looped back at the protocol layer (OSI Level 4), rather than at the
      driver layer (OSI Level 2).

      Only SOCK_STREAM is supported in the AF_UNIX address family.

      The HP-UX implementation of the local communication domain protocol
      does not support the MSG_OOB flag in recv() (see recv(2)) and send()
      (see send(2)).

    Addressing
      AF_UNIX socket addresses are path names.	They are limited to 92 bytes
      in length, including a terminating null byte.  Calls to bind() to an
      AF_UNIX socket utilize an addressing structure called
      structsockaddr_un (see bind(2)).	Pointers to this structure should be
      used in all AF_UNIX socket system calls wherever they require a
      pointer to a struct sockaddr.

      The include file <sys/un.h> defines this addressing structure.  Within
      this structure are two notable fields.  The first is sun_family, which
      must be set to AF_UNIX.  The next is sun_path, which is the null-
      terminated character string that specifies the path name of the file
      associated with the socket (for example, /tmp/mysocket).

      Only the passive (listening) socket must bind to an address.  The
      active socket connects to that address, but it does not need an
      address of its own.

      For additional information on using AF_UNIX sockets for interprocess
      communication, refer to the BSD Sockets Interface Programmer's Guide.

    Socket Buffer Size
      For stream and datagram sockets, the maximum send and receive buffer
      size is 262142 bytes.  The default buffer size is 32768 bytes.  The
      send and receive buffer sizes can be altered by using the SO_SNDBUF
      and SO_RCVBUF options of the setsockopt() system call.  Refer to
      getsockopt(2) for details.



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






 UNIX(7P)							    UNIX(7P)




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

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

















































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