In this JMessengerSC.rar include two folders:

1.Server:
--In this folder, you can find the RunServer.bat,this file is lunch the JMessenger Server,and run JMessenger Server before,you have to install the JRE.When you lunch the JMessenger Server in Dos mode, you can use this syntax, 

ex. "java JMessengerServer 6314" 

to lunch server.

The 6314 is the server port, you can set to other number for your server.

2.Client:
--In this folder,You can double click the jMessengerW.exe to run Client.The first,set your name in client,and if IP and Port fields by default, you just press Connection button to connect the server.and you can type the text to send other client.

--You can double click jMessengerW.exe again to simulate your other friend.