Launching a Citrix XenApp 6.5 application published through a Citrix Access Gateway throws the error: “Unable to launch your application. Contact your help desk with the following information: Cannot connect to the Citrix XenApp server. Socket operation on non-socket.”

Problem

You attempt to launch a Citrix XenApp 6.5 application published through a Citrix Access Gateway but the Citrix Receiver throws the error:

Unable to launch your application. Contact your help desk with the following information: Cannot connect to the Citrix XenApp server. Socket operation on non-socket.

Solution

While there are probably various reasons why this error will be thrown but the one of the reasons are describe in the following KB:

Error: "Unable to launch your application." Appears When you Launch Published Applications
http://support.citrix.com/article/CTX134940

While the Maximum Number of Users on the CAG I was working with was set correctly, I noticed that the Virtual Server mode was set to SmartAccess Mode:

Switching it to Basic Mode: