Connect to GNOME Display Manager (GDM) using XMing X Server for Windows

The GDM display manager implements all significant features required for managing attached and remote displays.

The GDM daemon can be configured to listen for and manage X Display Manage Protocol (XDMCP) requests from remote displays.

GDM has a number of configuration interfaces. These include scripting integration points, daemon configuration, greeter configuration, general session settings, integration with gnome-settings-daemon configuration, and session configuration.
By default XDMCP support is turned off, but can be enabled if desired.



Daemon Configuration for XDMCP

The GDM daemon is configured using the /etc/gdm/custom.conf file. Default values are stored in GConf in the gdm.schemas file. It is recommended that end-users modify the /etc/gdm/custom.conf file because the schemas file may be overwritten when the user updates their system to have a newer version of GDM.

Note that older versions of GDM supported additional configuration options which are no longer supported in the latest versions of GDM.

The /etc/gdm/custom.conf supports the "[daemon]", "[security]", and "[xdmcp]" group sections

To enable XDMCP Support add the following in custom.conf file

[xdmcp]
Enable=true

[security]
DisallowTCP=false
AllowRemoteRoot=true

Restart X Windows using the command gdm-restart

Connecting to GDM through XMing X Server

Step1: Download XMing X Server executable for Windows from here and install it.

Step2: Launch XLaunch. Select Fullscreen


Step3: Select Open Session via XDMCP


Step4: Enter hostname or ip address


Step5: Click Next


Step6: Click Finish


Step7: You have successfully connected through XMing



References:
1. GNOME Documentation
2. Comparing XDM, GDM, KDM and WDM