unix(7p) [hpux man page]

UNIX(7P)																  UNIX(7P)

NAME

       UNIX - local communication domain protocol

SYNOPSIS

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 address family.  This protocol can be used as an alternative to the Internet protocol family (TCP/IP or UDP/IP) for communi-
       cation  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 is supported in the address family.

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

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

       The  include file defines this addressing structure.  Within this structure are two notable fields.  The first is sun_family, which must be
       set to 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,

       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 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 and options of the system call.  Refer to getsockopt(2) for details.

AUTHOR

       was developed by the University of California, Berkeley.

SEE ALSO

       getsockopt(2), socket(2).

																	  UNIX(7P)

UNIX(4) 						   BSD Kernel Interfaces Manual 						   UNIX(4)

NAME

     unix -- UNIX-domain protocol family

SYNOPSIS

     #include <sys/types.h>
     #include <sys/un.h>

DESCRIPTION

     The UNIX-domain protocol family is a collection of protocols that provides local (on-machine) interprocess communication through the normal
     socket(2) mechanisms.  The UNIX-domain family supports the SOCK_STREAM and SOCK_DGRAM socket types and uses file system pathnames for
     addressing.

ADDRESSING

     UNIX-domain addresses are variable-length file system pathnames of at most 104 characters.  The include file <sys/un.h> defines this address:

	   struct sockaddr_un {
		   u_char  sun_len;
		   u_char  sun_family;
		   char    sun_path[104];
	   };

     Binding a name to a UNIX-domain socket with bind(2) causes a socket file to be created in the file system.  This file is not removed when the
     socket is closed -- unlink(2) must be used to remove the file.

     The length of UNIX-domain address, required by bind(2) and connect(2), can be calculated by the macro SUN_LEN() defined in <sys/un.h>.  The
     sun_path field must be terminated by a NUL character to be used with SUN_LEN(), but the terminating NUL is not part of the address.

     The UNIX-domain protocol family does not support broadcast addressing or any form of ``wildcard'' matching on incoming messages.  All
     addresses are absolute- or relative-pathnames of other UNIX-domain sockets.  Normal file system access-control mechanisms are also applied
     when referencing pathnames; e.g., the destination of a connect(2) or sendto(2) must be writable.

PROTOCOLS

     The UNIX-domain protocol family is comprised of simple transport protocols that support the SOCK_STREAM and SOCK_DGRAM abstractions.
     SOCK_STREAM sockets also support the communication of UNIX file descriptors through the use of the msg_control field in the msg argument to
     sendmsg(2) and recvmsg(2).

     Any valid descriptor may be sent in a message.  The file descriptor(s) to be passed are described using a struct cmsghdr that is defined in
     the include file <sys/socket.h>.  The type of the message is SCM_RIGHTS, and the data portion of the messages is an array of integers repre-
     senting the file descriptors to be passed.  The number of descriptors being passed is defined by the length field of the message; the length
     field is the sum of the size of the header plus the size of the array of file descriptors.

     The received descriptor is a duplicate of the sender's descriptor, as if it were created with a call to dup(2).  Per-process descriptor
     flags, set with fcntl(2), are not passed to a receiver.  Descriptors that are awaiting delivery, or that are purposely not received, are
     automatically closed by the system when the destination socket is closed.

     The effective credentials (i.e., the user ID and group list) of a peer on a SOCK_STREAM socket may be obtained using the LOCAL_PEERCRED
     socket option.  This may be used by a server to obtain and verify the credentials of its client, and vice versa by the client to verify the
     credentials of the server.  These will arrive in the form of a filled in struct xucred (defined in <sys/ucred.h>).  The credentials presented
     to the server (the listen(2) caller) are those of the client when it called connect(2); the credentials presented to the client (the
     connect(2) caller) are those of the server when it called listen(2).  This mechanism is reliable; there is no way for either party to influ-
     ence the credentials presented to its peer except by calling the appropriate system call (e.g., connect(2) or listen(2)) under different
     effective credentials.

     UNIX domain sockets support a number of socket options which can be set with setsockopt(2) and tested with getsockopt(2):

     LOCAL_CREDS     This option may be enabled on a SOCK_DGRAM or a SOCK_STREAM socket.  This option provides a mechanism for the receiver to
		     receive the credentials of the process as a recvmsg(2) control message.  The msg_control field in the msghdr structure points
		     to a buffer that contains a cmsghdr structure followed by a variable length sockcred structure, defined in <sys/socket.h> as
		     follows:

		     struct sockcred {
		       uid_t sc_uid;	     /* real user id */
		       uid_t sc_euid;	     /* effective user id */
		       gid_t sc_gid;	     /* real group id */
		       gid_t sc_egid;	     /* effective group id */
		       int   sc_ngroups;     /* number of supplemental groups */
		       gid_t sc_groups[1];   /* variable length */
		     };

		     The SOCKCREDSIZE() macro computes the size of the sockcred structure for a specified number of groups.  The cmsghdr fields
		     have the following values:

		     cmsg_len = CMSG_LEN(SOCKCREDSIZE(ngroups))
		     cmsg_level = SOL_SOCKET
		     cmsg_type = SCM_CREDS

     LOCAL_CONNWAIT  Used with SOCK_STREAM sockets, this option causes the connect(2) function to block until accept(2) has been called on the
		     listening socket.

SEE ALSO

     socket(2), intro(4)

     "An Introductory 4.3 BSD Interprocess Communication Tutorial", PS1, 7.

     "An Advanced 4.3 BSD Interprocess Communication Tutorial", PS1, 8.

BSD
								   July 15, 2001							       BSD