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home | helpx minix x x minixx X25(7) Linux Programmer's Manual X25(7) NAME x25 - ITU-T X.25 / ISO-8208 protocol interface. SYNOPSIS #include <sys/socket.h> #include <linux/x25.h> x25_socket = socket(AF_X25, SOCK_SEQPACKET, 0); DESCRIPTION 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 recommenda- tion X.25 (X.25 DTE-DCE mode). X25 sockets can also be used for commu- nication 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 re- trieve the same chunk of data as output with the corresponding write(2) to the peer socket. When necessary, the kernel takes care of segment- ing and reassembling long messages by means of the X.25 M-bit. There is no hard-coded upper limit for the message size. However, reassem- bling of a long message might fail if there is a temporary lack of sys- tem resources or when other constraints (such as socket memory or buf- fer size limits) become effective. If that occurs, the X.25 connection will be reset. Socket addresses The AF_X25 socket address family uses the struct sockaddr_x25 for rep- resenting 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 null byte) ASCII characters forming the X.121 address. Only the decimal digit characters from '0' to '9' are al- lowed. Socket options The following X.25-specific socket options can be set by using setsock- opt(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 accessi- ble 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 addi- tional 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. VERSIONS The AF_X25 protocol family is a new feature of Linux 2.2. BUGS 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_EXPERI- MENTAL 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. SEE ALSO 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>. COLOPHON This page is part of release 5.05 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. Linux 2017-09-15 X25(7)
NAME | SYNOPSIS | DESCRIPTION | VERSIONS | BUGS | SEE ALSO | COLOPHON