Users trying to launch the desktop enabling the "HDX Adaptive Transport" policy set to Diagnostic and it fails with the following error:

Unable to connect to the server. Contact your system administrator with the following error: There is no Citrix XenApp server configured on the specified address. (Socket Error 10060)

• When set to Preferred, data transport over EDT is used as primary and fallback to TCP. By default, adaptive transport is disabled (Off) and TCP is always used.
• For testing purposes, you can set Diagnostic mode, in which case only EDT is used, and fallback to TCP is disabled. 

1. First, test with policy set to Preferred.  [No UDP Ports are opened]
   1. Launch the Desktop.
   2. From command prompt browse to "C:\Program Files (x86)\Citrix\System32" 
   3. Run 'CtxSession'

• You can see that TCP is being used with CGP (Session Reliability) and Session Reliability encapsulates the ICA protocol.

2. Run CtxSession /v for a verbose output. Here you can see the port 2598 being used on the VDA.

3. Now set the policy to 'Diagnostic mode'.

• Ensure UDP 1494 and 2598 ports open on the VDA I connect back to the Citrix desktop, run CtxSession /v and receive confirmation that we are now using UDP 2598. This means that HDX Enlightened Data Transport is being used with Session Reliability. You can also check Director and note the protocol will be set as UDP.

Problem Cause