The best approach is to add the second port to the Sybase server and then push out the second port to the Global interfaces file via push and then monitor if the old one is still being used, once it is no longer used it can be dropped. Below are the detailed steps for doing this:

Add the new port with the following command sp_listener ‘start’, ‘protocol:host:port’
e.g. sp_listener start, ‘tcp:camifxlddb01.gbcaydc.baml.com:50000’

Update the local interfaces file for the Sybase Server to add the second port, so that it gets loaded at next restart. You’ll also need to update any other local interface entries for this server, like replication server etc.

The usage of the new port can be checked with the query:
select Login, Application, ClientHost, ListenerPort, getdate() as ‘Collection_Date’
from master..monProcessLookup
where Login is not null
and ListenerPort=<port number>

When you are happy simply, shut down the server, remove the old port from the interfaces file and restart the Sybase server.