xpamethod(n) SAORD Documentation xpamethod(n)
XPAMethod: XPA Communication Methods
XPA supports both inet and unix (local) socket communication.
XPA uses sockets for communication between processes. It supports three
methods of socket communication: inet, localhost, and unix. In general,
the same method should be employed for all XPA processes in a session
and the global environment variable XPA_METHOD should be used to set up
the desired method. By default, the preferred method is "inet", which
is appropriate for most users. You can set up a different method by
typing something like:
setenv XPA_METHOD local # unix csh
XPA_METHOD=local; export XPA_METHOD # unix sh, bash, windows/cygwin
set XPA_METHOD=localhost # dos/windows
The options for XPA_METHOD are: inet, unix (or local), and localhost.
On Unix machines, this environment setup command can be placed in your
shell init file (.cshrc, .profile, .bashrc, etc.) On Windows platforms,
it can be placed in your AUTOEXEC.BAT file (I think!).
By default, inet sockets are used by XPA. These are the standard
Internet sockets that are used by programs such as Netscape, ftp. etc.
Inet sockets utilize the IP address of the given machine and a (usually
random) port number to communicate between processes on the same
machine or between different machines on the Internet. (Note that XPA
has an Access Control mechanism to prevent unauthorized access of XPA
access points by other computers on the Net). For users connected to
the Internet, this usually is the appropriate communication method. For
more information about setting up XPA communication between machines,
see Communication Between Machines.
In you are using XPA on a machine without an Internet connection, then
inet sockets are not appropriate. In fact, an XPA process often will
hang for many seconds while waiting for a response from the Domain Name
Service (DNS) when using inet sockets. Instead of inet sockets, users
on Unix platforms can also use unix sockets (also known as local
sockets). These sockets are based on the local file system and do not
make use of the DNS. They generally are considered to be faster than
inet sockets, but they are not implemented under Windows. Use local
sockets as a first resort if you are on a Unix machine that is not
connected to the Internet.
Users not connected to the Internet also can use localhost sockets.
These are also inet-type sockets but the IP address used for the local
machine is the localhost address, 0x7F000001, instead of the real IP of
the machine. Depending on how sockets are set up for a given platform,
communication with the DNS usually is not required in this case (though
of course, XPA cannot interact with other machines). The localhost
method will generally work on both Unix and Windows platforms, but
whether the DNS is required or not is subject to individual
A final warning/reminder: if your XPA-enabled server hangs at startup
time and your XPA_METHOD is inet, the problem probably is related to an
incorrect Internet configuration. This can be confirmed by using the
unix method or (usually) the localhost method. You can use these
alternate methods if other hosts do not need access to the XPA server.
See xpa(n) for a list of XPA help pages
version 2.1.15 July 23, 2013 xpamethod(n)