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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 <ProjectRoot>/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 <ProjectRoot>/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.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABIL-
ITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.
Except as contained in this notice, the name of the X Consortium shall
not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization from
the X Consortium.
X Window System is a trademark of X Consortium, Inc.
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