path: root/README

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 Netscape	Naviga-
tor plug-in (libxrx) that demonstrate this protocol.  The plug-in
requires Navigator 3.0.

We have	only been able to test the plug-in on HP-UX, IRIX, Digital Unix,
and Solaris2.  Netscape	Navigator binaries for other platforms are
either not available at	all or were not	available in time to be	included
in the testing for this	release.

The specification for the RX mime type is in xc/doc/specs/RX/RX.mif
(FrameMaker interchange	source)	and xc/doc/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 Netscape 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.

If you don't currently have a web server the NCSA server is a good one
to try.	 Binaries for various systems are available at:

     http://hoohoo.ncsa.uiuc.edu/docs/setup/PreExec.html

If you don't have perl you can get the source code from:
     ftp://prep.ai.mit.edu/pub/gnu/perl-4.036.tar.gz

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 adding the	following definitions to your site.def or
host.def file:


WebServer      defines the hostname and	port of	your web server, for
	       example

	       #define WebServer www.myorg.org:8001

HtmlDir	       defines the path	at which HTML and RX documents are
	       installed, for example

	       #define HtmlDir /usr/local/etc/httpd/htdocs

CgiBinDir      defines the path	at which CGI programs are installed, for
	       example

	       #define CgiBinDir /usr/local/etc/httpd/cgi-bin

ProxyManager   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:

	       #define ProxyManager tcp/www.myorg.org:6500

Then make the Makefiles	and build the directories with the following
command	sequence:

cd xc/programs/xrx/htdocs
xmkmf ../../.. programs/xrx/htdocs
make
make install
cd ../cgi-bin
xmkmf ../../.. programs/xrx/cgi-bin
make
make install


These directories are not automatically	built or installed by the top
level Makefile because they install outside the	ProjectRoot.

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 Netscape Navigator Plug-in


The Navigator plug-in supports all the functions of xrx	and in addition
uses the new 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 be able to use the RX plug-in you need Netscape Navigator 3.0.
Binaries for various systems can be found at:

     http://home.netscape.com/comprod/mirror/client_download.html

To complete the	installation of	the Netscape plug-in, find the file
named libxrx.so.6.3 or libxrx.sl.6.3 (or similar, depending on your
platform) in <ProjectRoot>/lib (e.g. /usr/X11R6.3/lib) and copy	it to
either /usr/local/lib/netscape/plugins or $HOME/.netscape/plugins. Do
not install the	symlinks libxrx.so or libxrx.sl; they may confuse
Netscape.

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 Netscape Navigator, you need	to exit	and res-
tart 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/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 Netscape Navigator 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 Netscape Navigator 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.


------------------------------------------------------------------------------
This text originally came from "X Window System, Version 11, Release 6.3
Release Notes", which were covered by the following notice:

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