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23. How to determine the value of an XTI address string


This information is not applicable to Win32 systems.

Most modern UNIX systems provide support for the socket network interface. Most people will build Distributed TETware to use the socket network interface and so don't need to be concerned about XTI addresses. The information presented in this article might be useful if you have to set up Distributed TETware to use the XTI network interface for some reason.


Where does TETware use an XTI address string?

When Distributed TETware is built to use the XTI network interface you have to specify an XTI address string in the following places:

  1. tccd must be invoked with a -p option which tells it on which network end point to listen.

  2. For each entry in the systems file you must provide a third field that specifies the XTI address that can be used to connect to tccd on that system.

XTI address strings

An XTI address string consists of a sequence of 2-digit hexadecimal values. When TCP is the transport provider, these values often represent a dump of a sockaddr_in structure which describes the network address.

For example, consider the following definitions taken from <netinet/in.h> on a hypothetical machine:

struct in_addr {
	unsigned long s_addr;

struct sockaddr_in {
	short sin_family;
	unsigned short sin_port;
	struct in_addr sin_addr;
	char sin_zero[8];

Suppose that on this machine:
  • a short is 16 bits wide

  • a long is 32 bits wide

  • structure members are aligned on 2-byte boundaries (so there will be no padding between members in the sockaddr_in structure)

It can be seen that the format of an XTI address string on this machine will be:
where FFFF is the address family (in host byte order) PPPP is the port number (in network byte order) and AAAAAAAA is the IP address (also in network byte order).

tccd -p option

In most cases you want tccd to accept connections on all network interfaces, so you need to specify the IP address as INADDR_ANY (value zero on many systems).

Suppose that:

  • the byte order of the machine is high byte first (big-endian)

  • you decide to use port 7500 as the well-known port

  • the name of the transport provider is /dev/tcp

You would invoke tccd as follows:

tccd -p 00021d4c000000000000000000000000 -M TCP -P /dev/tcp [ other-options . . .]

This XTI address string can be read as follows:


The address family (AF_INET - value 2 on many systems)


The port number to listen on (7500 decimal is 0x1d4c hex)


The IP address to use (INADDR_ANY - value zero on many systems)


Zero-filled padding (char sin_zero[8])

Note that the IP address and port number are in network byte order. So on a little-endian machine the only thing that changes is the address family. For example:

tccd -p 02001d4c000000000000000000000000 -M TCP -P /dev/tcp [ other-options . . .]

systems file

The XTI address in a systems file entry is constructed in the same way as for tccd except it is necessary to specify a real IP address instead of INADDR_ANY. Foe example, suppose you decide to use a machine called fred as system 1. The IP address of fred is and tccd is listening on port 7500. The systems file entry would look like this:

001	fred	00021d4c5900ad180000000000000000

This XTI address string can be read as follows:


The address family (AF_INET - value 2 on many systems)


The port number to listen on (7500 decimal is 0x1d4c hex)


The IP address to use ( is 0x5900ad18 hex)


Zero-filled padding (char sin_zero[8])

See also

  • "Systems definitions'' in the TETware Programmers Guide.

  • The systems and tccd manual pages in the TETware User Guide.


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