NAME | SYNOPSIS | DESCRIPTION | VERSIONS | BUGS | SEE ALSO | COLOPHON
X25(7) Linux Programmer's Manual X25(7)
x25, AF_X25 - ITU-T X.25 / ISO-8208 protocol interface.
#include <sys/socket.h>
#include <linux/x25.h>
x25_socket = socket(AF_X25, SOCK_SEQPACKET, 0);
X25 sockets provide an interface to the X.25 packet layer protocol. This
allows applications to communicate over a public X.25 data network as
standardized by International Telecommunication Union's recommendation X.25
(X.25 DTE-DCE mode). X25 sockets can also be used for communication without
an intermediate X.25 network (X.25 DTE-DTE mode) as described in ISO-8208.
Message boundaries are preserved -- a read(2) from a socket will retrieve the
same chunk of data as output with the corresponding write(2) to the peer
socket. When necessary, the kernel takes care of segmenting and re-assembling
long messages by means of the X.25 M-bit. There is no hard-coded upper limit
for the message size. However, re-assembling of a long message might fail if
there is a temporary lack of system resources or when other constraints (such
as socket memory or buffer size limits) become effective. If that occurs, the
X.25 connection will be reset.
The AF_X25 socket address family uses the struct sockaddr_x25 for representing
network addresses as defined in ITU-T recommendation X.121.
struct sockaddr_x25 {
sa_family_t sx25_family; /* must be AF_X25 */
x25_address sx25_addr; /* X.121 Address */
};
sx25_addr contains a char array x25_addr[] to be interpreted as a null-
terminated string. sx25_addr.x25_addr[] consists of up to 15 (not counting
the terminating 0) ASCII characters forming the X.121 address. Only the
decimal digit characters from '0' to '9' are allowed.
The following X.25-specific socket options can be set by using setsockopt(2)
and read with getsockopt(2) with the level argument set to SOL_X25.
X25_QBITINCL
Controls whether the X.25 Q-bit (Qualified Data Bit) is accessible by
the user. It expects an integer argument. If set to 0 (default), the
Q-bit is never set for outgoing packets and the Q-bit of incoming
packets is ignored. If set to 1, an additional first byte is prepended
to each message read from or written to the socket. For data read from
the socket, a 0 first byte indicates that the Q-bits of the
corresponding incoming data packets were not set. A first byte with
value 1 indicates that the Q-bit of the corresponding incoming data
packets was set. If the first byte of the data written to the socket
is 1 the Q-bit of the corresponding outgoing data packets will be set.
If the first byte is 0 the Q-bit will not be set.
The AF_X25 protocol family is a new feature of Linux 2.2.
Plenty, as the X.25 PLP implementation is CONFIG_EXPERIMENTAL.
This man page is incomplete.
There is no dedicated application programmer's header file yet; you need to
include the kernel header file <linux/x25.h>. CONFIG_EXPERIMENTAL might also
imply that future versions of the interface are not binary compatible.
X.25 N-Reset events are not propagated to the user process yet. Thus, if a
reset occurred, data might be lost without notice.
socket(2), socket(7)
Jonathan Simon Naylor: "The Re-Analysis and Re-Implementation of X.25." The
URL is
ftp://ftp.pspt.fi/pub/ham/linux/ax25/x25doc.tgz
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-08-08 X25(7)