It seems that the client communication is customized on a different port.
As per Version is 11.0.6005 browse to following location :- C:\Program Files\Symantec\Symantec Endpoint Protection and look for sylink.xml.
This file is used for communication between SEPM and clients. When you open the file which would open is a web page (IE) by default, that would give us more info about which port client communication is configured on.
If possible could you upload sylink.xml file to confirm the same
Cheers!!