If you register a new server in Caché Monitor the default Port is 1972. This can be the wrong port! If you get a "Communication link failure", please check the port first. You can do that by open the "Server properties" dialog:

Here are some Information about the new port handling in Caché 2007.1:

Caché 2007.1 chooses the default ports for installation differently from previous releases. The new algorithm is:  If port 1972 is unused, choose it. Otherwise, choose the first available port number equal to or greater than 56773.

Caché 5.2 does it in this way:  Use 1972 or the first available subsequent number.