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  From: Martin Sandiford <ms@mcdev.com.au>
  To  : Sulis, Adam" <SULISA@tc.gc.ca>, Linux SA <SULISA@tc.gc.ca>
  Date: 17 Sep 1999 12:00:17 +0930

Re: Confiuring XDMCP Broadcast

(Sorry for previous incomplete email - finger problem)

>>>>> "Adam" == Sulis, Adam <SULISA@tc.gc.ca> writes:

    Adam> Hi group: I have installed XWin32 for Windows 95, and am
    Adam> trying to connect to a Redhat 6 box. I would like to be able
    Adam> to:

    Adam> 1. Have the box show up on the XDMCP Selector list
    Adam> 2. Run a full desktop session on XWin32 (RSH, single window)

These seem to be different things.  If you are using XDMCP, you do not
need to use rsh to login.

You will need to start xdm (or on redhat 6, /etc/X11/prefdm).

You can then use the XDMCP option with X-Win32 to connect to the Linux
box.

There are normally three ways that you can connect to an xdm server
using an X server:

1. Specify the IP address of the xdm server you wish to connect to (aka
"query" mode).  If all is well, a login window will be displayed on the
X server, and you will be logged into the xdm server.  You need to
specify the IP of the xdm server to log in to.

2. Use broadcast mode, where the X server sends out broadcast requests
to connect to an xdm server.  The first xdm server that responds is the
one you get a login window for. You do not need to specify IP addresses.

3. Use "indirect" mode, where the X server requests that xdm server to
run a "chooser" which displays a list of hosts that you can log in to
with xdm.  You then choose one, and are logged in.  You will need to
specify the IP address of the xdm server which will display the chooser.

If you are using RH6 and gnome, then you are probably using gdm.  I have 
not been able to get gdm to display a chooser for indirect mode, but I
have been able to get xdm to work fine.  If you wish to try with xdm,
you can "cd /etc/X11" and then "ln -sf /usr/X11R6/bin/xdm prefdm".

I believe that XWin32 supports all of these options under the session
setup (?).

    Adam> Here are my observations so far (thanks to the archive for
    Adam> reference):

    Adam> 1. I can get applications up by manually initiating a remote
    Adam> login: - Double-Click XWin32 - telnet to the Redhat box (in
    Adam> my case 1.2.3.1) - log in as root - issue "export
    Adam> DISPLAY=1.2.3.2:0.0" where 1.2.3.2 is the 95 box - issue
    Adam> "xcalc" (or xterm, netscape, or other x app)

Good - pretty much all the components are working.

    Adam> 2. I modified the /etc/X11/xdm/Xservers file as follows:
    Adam> changed: :0 local /usr/X11R6/bin/X to: :0 local
    Adam> /usr/X11R6/bin/X -broadcast and restarted the box hoping
    Adam> that would cause the broadcast.

This is probably not what you want.  Xdm will start local server(s) and
show login windows on them if you wish.  If you do not need a local
server, then comment this line out. In any case, you do not need the
-broadcast.  -broadcast asks the local X server to connect to an xdm
server, which happens automagically for servers started by xdm anyway.

If you do not want to have X started automatically on the linux box, you 
can comment this line out altogether.

    Adam> The Redhat box is configured with defaults, and works with
    Adam> manual login, so I suspect that I have to alter the server
    Adam> parms to allow XDMCP broadcasts.

Yes, but probably on the X server, not the xdm server.  Have a look in
the XWin32 setup options for XDMCP stuff. This is what you want.  Also
read above about gdm vs xdm.

A word of caution: the /etc/X11/xdm/Xaccess file specifies who will be
able to get a login window and/or a chooser from your xdm server.  As
shipped, RH6 allows *anyone* to get a login and/or chooser.  Some people
may consider this a security flaw.

    Adam> I am having trouble finding documentation to RTFM. Perhaps
    Adam> if someone could point me in the right direction. This would
    Adam> make an excellent HOWTO.

/usr/doc/HOWTO/mini/Remote-X-Apps is a good place to start.

    Adam> Any hints would be appreciated by this newbie.

Cheers,
Martin

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