When you try to connect to an XDMCP session from Xbrowser, Xmanager displays grey background and XDMCP connection fails after awhile. And, Xmanager log file shows:

Xdmcp Request Address: 192.168.1.5
Xdmcp Connection Address 0: 192.168.1.4
Xdmcp: sent a REQUEST message
Xdmcp: received an ACCEPT message
Xdmcp: sent a MANAGE message.
Xdmcp: Timed out, state 8. Retransmissions: 0
Xdmcp: sent a MANAGE message.
Xdmcp: Timed out, state 8. Retransmissions: 1
Xdmcp: sent a MANAGE message.
Xdmcp: Timed out, state 8. Retransmissions: 2
Xdmcp: sent a MANAGE message.
Xdmcp: received a FAILED message.
Xdmcp fatal error: Session failed Session 86 failed for display example.domain.com:0: Cannot open display

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



This problem is usually caused by one of the following reasons:

1. Firewall settings on PC, physical firewall, gateway or router.
2. Incorrect entry in the DNS.
3. Improper operation of display manager such as gdm, kdm or xdm.

For each case, try the following solutions:

Firewall settings on PC, physical firewall, gateway or router 
Follow the instruction on Xmanager FAQ and configure your firewall.

http://www.netsarang.com/faq/xmanager/3161

Incorrect entry in the DNS
Add your PC IP address in /etc/hosts as following:

     172.16.2.120 PC_NAME

Improper operation of display manager such as gdm, kdm or xdm.
Restart the display manager process. You can also restart the remote server.