RX: X Remote eXecution ---------------------- The remote execution (RX) service specifies a MIME format for invoking applications remotely, for example via a World Wide Web browser. This RX format specifies a syntax for listing network services required by the application, for example an X display server. The requesting Web browser must identify specific instances of the services in the request to invoke the application. The distribution contains a helper program (xrx) and a Mozilla family browser plug-in (libxrx) that demonstrate this protocol. The plug-in was originally written for Navigator 3.0, but has been used with later versions of the Mozilla family of browsers, including Firefox. The specification for the RX mime type is in the xorg-docs module in the X.Org repository in specs/RX/RX.mif (FrameMaker interchange source) and hardcopy/RX/RX.PS.Z (compressed PostScript). The following section describes the procedure to set up your environment and try the examples provided in this distribution. 1. Preparing Your Web Server In order to demonstrate the RX helper program and the RX browser plug-in you need to have access to an HTTP server to install ``common gateway interface'' (CGI) scripts. While CGI programs can be written in any compiled or interpreted language, the sample CGI programs in the distri- bution are written in perl. You need to install the HTML, RX, and CGI sample files into your server's HTML and CGI directories. The process can be partially automated by replacing the following tokens in the files in the htdocs and cgi-bin directories: XPROJECT_ROOT the prefix under which your X applications are installed, for example: /usr/X11 WEBSERVER defines the hostname and port of your web server, for example: www.myorg.org:8001 CGIBINDIR defines the path at which CGI programs are installed, for example: /usr/local/etc/httpd/cgi-bin XPROXYMNGR defines the transport scheme, hostname, and port for CGI programs to contact the Proxy Manager. See the proxymngr man pages for further details. Typically the proxy manager host will be the same as your web server, for example: tcp/www.myorg.org:6500 You may need to change the path to the perl command in the first line of the cgi-bin scripts if it is not installed in /usr/local/bin/perl on your system. You also need to configure your web server so that files with the exten- sion name ``rx'' are of the MIME type ``application/x-rx''. See your HTTP server's configuration documentation for the right procedure to do so. 2. The RX Helper Program The helper program, xrx, may be used with any Web browser to interpret the new RX document type. The RX helper program is installed in /bin (e.g. /usr/X11R6.3/bin/). You will need to configure your web browser to use it for RX documents by adding a line to your $HOME/.mailcap: application/x-rx; /X11/bin/xrx %s You may need to refer to your web browser's documentation for exact instructions on configuring helper applications. The helper program is activated by your browser as soon as you retrieve any document of the MIME type application/x-rx. All you need to do is to point your browser at the URL: http://your.web.server/xload.rx The application (i.e. xload) should appear on your DISPLAY as a new top-level client. The client will be running on your web server host and connected to your X server. If your X server supports the SECURITY extension the client will be running as an untrusted client. 3. The RX Browser Plug-in The browser plug-in supports all the functions of xrx and in addition uses the XC-APPGROUP extension, if your X server provides it, to cause the remotely launched application to be embedded within the browser page from which it was launched. The HTML page links to an RX document via the EMBED tag, a Netscape extension to HTML. The RX document provides the plug-in with the list of services the application wants to use. Based on this information, the plug-in sets the various requested services, including creating authorization keys, and passes the relevant data 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. To complete the installation of the Netscape plug-in, find the file named libxrx.so or libxrx.sl (or similar, depending on your platform) in /lib (e.g. /usr/X11R6.3/lib) and copy it to the browser plugin directory in the system installation or your home directory (such as /usr/lib/firefox/plugins or $HOME/.mozilla/plugins). You should 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 the web browser, 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 the browser has successfully loaded the plug-in by checking the ``About Plug-ins'' page from the Help menu or the about:plugins URL. This should show something like: RX Plug-in File name: /usr/guest/netscape/plugins/libxrx.sl.6.3 X Remote Activation Plug-in Mime Type Description Suffixes Enabled application/x-rx X Remote Activation Plug-inxrxYes The plug-in will be activated by the browser as soon as you retrieve any document of the MIME type application/x-rx. Several sam- ples are included in the distribution. The most basic one is xload. All you need to do is point your browser at the page: http://your.web.server/xload.html If something goes wrong check on the all the previous steps listed above and try again. Once xload is working you can try some of the other examples in the distribution such as bitmap.html or dtcm.html. 4. Trying Embedding With an Old X Server The browser plug-in, libxrx, will work with an X server that does not contain the application group or security extensions. The application will be started as a separate top-level client. If you wish to try out the embedding facilities without replacing your desktop X server, you may use the Xnest server. A typical Xnest session would look like the following: % Xnest :11 % xterm -display :11 These two commands start a ``nested'' server and a terminal emulator within that server. Your favorite window manager and Netscape Navigator can now be executed from the nested xterm window. You may wish to first disable access control in the nested server by running ``xhost +'' in the nested xterm. 5. Setting Up Your Own Applications To Run Over The Web Based on the examples provided in the distribution it should be easy to set up your web server to run your own applications. Every application requires 3 additional files to identify it to Web browsers: myapp.html An HTML page to present the application embedded myapp.rx The RX document describing the application myapp.pl The CGI script to start the application Note that the separate ``.rx'' file could be omitted by implementing the CGI script such that if it is invoked without a QUERY_STRING it will return the RX content. We decided not to do so in the distributed exam- ples for purpose of clarity. The xload demo provides a good starting point. Simply make a copy of each of the files xload.rx, xload.html, and xload.pl. Then look inside them for every instance of ``xload'' and change it to whatever is appropriate for your application. You will not be able to run the dtcm demo unless you have dtcm (a CDE component) installed on your web server host. This example shows how a CGI script would look when an X Print server is requested. The script dtcm.pl is, for that reason, slightly more complicated than other exam- ples. 6. More information Hummingbird has provided a site with more information and some live demos at http://www.broadwayinfo.com/ ------------------------------------------------------------------------------ This text originally came from "X Window System, Version 11, Release 6.3 Release Notes", which were covered by the following notice: Copyright 1996 X Consortium Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, dis- tribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the fol- lowing conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. 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