Hi Harish..I feel like you have distributed instance..anyways another way to verify is by checking the profiles, certainly ASCS instance profile won't be shown on RZ10 so follow the below steps..
Goto AL11(Directory Tcode)>>>>search for DIR_PROFILE>>>>double click and enter>>>>there will be many files>>>>>>search for a file which will have entry of "ms" (linux) or "messageserver"(windows)..so that profile should be your message servers profile..now the port will be maintained there for sure... or if you find the file then the FileName should have the port number.
hope helps you determining
However there is no hard n fast rule of message server port to be -1 than instance..in distributed system it can be assigned to any instances or dedicated..anyways you should not be worrying about the message server so much. However once determined you can use the msgsvr to do load balance and get data in SLD - good way to do - recco..
But you can still get data by just putting the gateway of the apps you are asking..
like Hostname: bla.com
gateway: sapgw35