The X Display Manager Control Protocol (XDMCP) is a standard way for X Servers to request login services from host computers. Mac X server software, like Mac X and eXodus, have not included support for XDMCP. This means that Mac users have had to go to extreme lengths to get Unix hosts like HPs, Silicon Graphics, and Suns to present a login screen or to configure a login environment that operates the same as a X Terminal or console display.
Mac XDM addresses this problem by providing a separate application that performs the XDMCP "handshake" with a X Windows host, requesting a login session on behalf of the Mac X server.
Usage
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Using XDM 1.0 is straightforward for most applications. Start up your X server (Mac X, for example). Then run the XDM application and select the "LookUp" button to search for hosts on your local area net that are able to provide login services via XDMCP. Select a host from the list and click "Connect". Once the XDM application has contacted the host, the status area will inform you that it's OK to quit XDM and switch to your X server. That's it.
The "Query" button will provide additional information in the status area if a host provides it. Clicking on the buttons that make up the Broadcast Address will allow you to reconfigure the address that XDM will transmit broadcast requests to. For a majority of users, the address will be configured correctly, using the broadcast mask already configured for MacTCP. In some environments you may need to change the mask.
Most users will find (unfortunately) that subnetted networks will not pass broadcast traffic across routers. If a host you want to connect to doesn't respond to the "LookUp" command, just type the host name in the edit field and click "Connect" as usual.
Version Info
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XDM is still beta software. If you use it and have suggestions or encounter unexpected "features", please forward comments to cshotton@oac.hsc.uth.tmc.edu.
1.0º2 - Fixes several bugs. XDM will now run in 32 bit mode and *should* work on systems with multiple monitors. Added a configurable broadcast address.
1.0º1 - Only ran on my machine. Most people reported ugly crashes. Sorry.
To Do
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XDM will ultimately support startup documents that will automatically connect to a specified host and request a login.
An option may be provided to launch a particular application after connecting to a host.
