What I am trying to know : I want to Load test a Windows application that is based on a client server protocol. Can I do it using Jmeter or LoadRunner ?
If YES : What other information do I need to give you for better understanding of my query?
Awaiting for your response.
Your ability to test is dependent upon the communications architecture of your application. LoadRunner supports many interfaces that it can collect straight out of the box whereas with JMETER you are going to have a more programmatic path.
It depends on what you want to test.
JMeter will let you test the client-server traffic and server behaviour under load. But you will have to code the tcp protocol for example if it's one like that (or http protocol ). It really depends on what kind of client server protocol your application, but if it's a binary based protocol then you will need to code or find a plugin that does the encoding/decoding.
Other test tool use a window capture based testing approach which can capture the location of clicks, this ca make them support more protocols as they just rely on client capture but can make scenarios less stable in time if for example button position moves. But sometimes you don't have the choice.