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Commands Reference, Volume 3

libxrx Command


RX Netscape Navigator Plug-in.


The RX Plug-in may be used with Netscape Navigator (3.0 or later) to interpret documents in the RX MIME type format and start remote applications.

The RX Plug-in reads an RX document, from which it gets the list of services the application wants to use. Based on this information, the RX Plug-in sets the various requested services, including creating authorization keys if your X server supports the SECURITY extension. It then passes the relevant data, such as the X display name, to the application through an HTTP GET request of the associated CGI script. The Web server then executes the CGI script to start the application. The client runs on the web server host connected to your X server. In addition when the RX document is used within the EMBED tag (a Netscape extension to HTML), the RX Plug-in uses the XC-APPGROUP extension, if it is supported by your X server, to cause the remote application to be embedded within the browser page from which it was launched.


To install the RX Plug-in so that Netscape Navigator can use it, find the file named libxrx.so in /usr/lib/X11 and copy it to either the system Netscape plugin directory or $HOME/.netscape/plugins. Do not install it as a symbolic link, this would confuse Netscape.

If you have configured Netscape Navigator to use the RX helper program (xrx), you must reconfigure it. Generally you simply need to remove or comment out the line you may have previously added in your mailcap file to use the RX helper program. Otherwise the plug-in will not be enabled. (The usual comment character for mailcap is #.) If you are already running Netscape Navigator, you need to exit and restart it after copying the plug-in library so the new plug-in will be found. Once this is done you can check that Navigator has successfully loaded the plug-in by checking the About Plug-ins page from the Help menu. This should show something like:

RX Plug-in
File name: /usr/local/lib/netscape/plugins/libxrx.sl.6.3
X Remote Activation Plug-in
Mime Type Description Suffixes   Enabled
application/x-rx   X Remote Activation Plug-in   xrx   Yes

Once correctly configured, Netscape Navigator will activate the RX Plug-in whenever you retrieve any document of the MIME type application/x-rx.


The RX Plug-in looks for resources associated with the widget netscape.Navigator (class Netscape.TopLevelShell) and understands the following resource names and classes:

xrxHasFirewallProxy (class XrxHasFirewallProxy)
Specifies whether an X server firewall proxy is running and should be used. Default is False.
xrxInternalWebServers (class XrxInternalWebServers)
The web servers for which the X server firewall proxy should not be used (only relevant when xrxHasFirewallProxy is "True"). Its value is a comma separated list of mask/value pairs to be used to filter internal web servers, based on their address. The mask part specifies which segments of the address are to be considered and the value part specifies what the result should match. For instance the following list:,

matches the address sets: 198.112.45.* and 198.112.46.*. More precisely, the test is (address and mask) == value.

xrxFastWebServers (class XrxFastWebServers)
The web servers for which LBX should not be used. The resource value is a list of address mask/value pairs, as previously described.
xrxTrustedWebServers (class XrxTrustedWebServers)
The web servers from which remote applications should be run as trusted clients. The default is to run remote applications as untrusted clients. The resource value is a list of address mask/value pairs, as previously described.


If the RX document requests X-UI-LBX service and the default X server does not advertise the LBX extension, the RX Plug- in will look for the environment variable XREALDISPLAY to get a second address for your X server and look for the LBX extension there. When running your browser through lbxproxy you will need to set XREALDISPLAY to the actual address of your server if you wish remote applications to be able to use LBX across the Internet.

If the RX document requests XPRINT service, the RX Plug-in will look for the variables XPRINTER, PDPRINTER, LPDEST, PRINTER, and XPSERVERLIST to get the printer name and X Print server address to use. Note that although this set of variables allows to specify more than one server and printer, only the first pair will be used.

Finally, if you are using a firewall proxy, RX Plug-in will look for PROXY_MANAGER to get the address of your proxy manager (see proxymngr). When not specified it will use :6500 as the default.

Related Information

The xrx command, lbxproxy command, and the proxymngr command.

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