How to make tshark consider tcp messages going through a particular port (other than 3868) as diameter in linux?

I have this setup where a diameter connection is established which uses a tcp port which is different than the default port 3868.I have to take a pcap and analyze the diameter messages.Now the problem is we can analyze the pcap in wireshark GUI where I can add the other port along with 3868 in the view ->preferences -> diameter,then it will consider messages at this port also as diameter but how can I do the same in tshark CLI,should I set it in services file (/root/wireshark_182/wireshark-1.8.2/services) ?