Error "Unable to launch your application. Cannot connect to the Citrix XenApp Server. Socket operation on non-socket" is displayed when launching apps from Web Interface or StoreFront.

Important! This article is intended for use by System Administrators. If you are experiencing this issue and you are not a System Administrator, contact your organization’s Help Desk for assistance and refer them to this article.

1. Change the Secure Ticket Authority (STA) listed in the StoreFront server from using the fully qualified domain name (FQDN) to the IP address of the XenApp server. If you are using FQDN then always verify that the name can be resolved to the correct IP address of the STA servers.
2. Verify that the FQDN name listed in the STA list in StoreFront is the correct FQDN.
3. If you are unable to resolve the FQDN then add a host record directly onto to the StoreFront server to bypass any issues with DNS.
4. If you made any changes to STA on one of the StoreFront servers then ensure that the changes are propagated to all the other StoreFront servers.
5. Verify if the Secure Gateway, Web Interface and XenApp are listening on the same ports using the following information:
   Note: When changes are made to the Secure Gateway server, it has to be restarted for the changes to take effect and this will disrupt the sessions of any currently connected users.
   • Secure Gateway: Run through the Secure Gateway Wizard and confirm that the STAs have the FQDN (or IP) and that the TCP port matches that of Web Interface and XenApp.
   • Web Interface: Under the setting for Secure Access, click next until you get to the specify Secure Ticket Authority settings windows and confirm that the STA URLs are using the correct port. If not, highlight the STA, click Edit and adjust the URL to reflect the correct port.
   •  XenApp: Open a command line and run the command netstat -ano to see if the XenApp server is listening on the same port which is configured on Secure Gateway and Web Interface. If not, run the commands:
     net stop w3svc (this will stop IIS)
     ctxxmlss /u (this will un-register the existing port in use)
     ctxxmlss /r"nn" ("nn" represents the port number which you wish to register. Type it without the quotation marks. For example - ctxxmlss /r8080)
     net start w3svc (this will restart IIS)
6. Complete the following troubleshooting steps on the ICA file that is received while launching an application:
   • Verify if the ICA file has internal server IP address rather than "gateway FQDN:443" information. 
   • Verify if the ICA file has NetScaler Gateway FQDN:443 as specified on StoreFront server in NetScaler Gateway settings: SSLProxyHost=gateway-fqdn:443
   • Verify that on NetScaler Gateway the STA server is added globally or under vserver, similar to what you have specified on StoreFront Gateway settings. STA should be added on NetScaler Gateway and StoreFront. STA status should show as up on NetScaler Gateway.
7. Examine for probable DNS issues. The backend server address should be resolvable from NetScaler Gateway. If not, try adding “A Record” on NetScaler Gateway under “DNS” option.
8. If users are not able to launch applications after upgrading Firefox to version 30.0, then refer to article CTX200200 - Unable to Launch Applications from Firefox 30.0
9. Check if any XenDesktop servers fail to work as an STA. Remove the failed XenDesktop server as an STA and add another XenDesktop server as STA.