When attempting to start applications from an iPad with iOS 5.x and Citrix Receiver 5.5.x through Citrix Access Gateway, application start fails with the following error message:

”Cannot Open Page. Safari could not open the page because the server stopped responding.”

Download and Install - Latest Citrix Receiver 

OR 

Workaround
If using previous versions of Receiver and you cannot install the latest version, complete the following steps:

1. Verify that certificates are valid.

2. Verify all STA’s are up and running.

3. Verify that port 1494 is open from your gateway and XenApp server.

4. For CAG verify that port ICA 1494 is in the Access Control list.

5. Take Network Traces to determine point of failure (Links are provided in Additional Resources section).

6. Isolate the environment to determine failing segment.

7. Test with a Stand Alone IIS Server with CSG/CAG and XenApp from a client within the same subnet. Bypass any other firewalls in environment.

Problem Cause

There have been changes to iOS 5 platform, which affect connectivity issues from the device.

Important Changes

• iOS 5’s TLS implementation has been upgraded to support the TLS protocol version 1.2 as opposed to TLS 1.0 that worked for previous iOS versions. http://developer.apple.com/library/ios/#technotes/tn2287/_index.html

• Support for X.509 certificates with a MD5 hash has been disabled for use as trusted certificate. http://support.apple.com/kb/HT4999

• Default system trust settings have been reconfigured to not trust Digicert issued certificates. http://support.apple.com/kb/HT5052

Note: If any of these configurations are in place in your network you will experience client authentication time-outs because of a failed SSL handshake.

CTX122965 - iPhone Receiver Error:ICA engine error 29 The SOCKS 5 handshake failed

http://developer.apple.com/library/ios/#technotes/tn2287/_index.html

http://support.apple.com/kb/HT5052

http://support.apple.com/kb/HT4999

https://developer.apple.com/library/ios/#qa/qa1176/_index.html