How to change the default UDP port (# 177) for XDMCP connection

PROBLEM DESCRIPTION

The following article explains how you can change the default port for the display manager on the remote server in case the default port is blocked by security policies, firewall or any other reasons.

The default port number for XDMCP connection is UDP port 177.

*This article requires remote server configuration. Administrator previlage may be required.

RESOLUTION

Step 1. Follow the instruction below for your display manager:

• If you use XDM, open the xdm.config file, and change the DisplayManager.requestPort value.
  
• If you use GDM, open the gdm.conf file, and change the Port value under the [xdmcp] section.
• If you use KDM, open the kdmrc file , change the Port value under the [xdmcp] section.
• If you use dtlogin, open the Xconfig file , change the Dtlogin.requestPort value.

Step 2. Once you change the default port on the remote server, you need to manually change the 'Port Number' option for XDMCP sessions on Xmanager. To do this:

1. Open Xmanager.
2. Right click on an XDMCP session and select Properties.
3. For Port Number, enter the port number used in Step 1.