Hi Radhika,
First of all i moved your thread to "New To Java" forum since it was not appropriate for "Java Announcements" forum.
Your problem has two parts:
1. Controlling serial port on a machine
For this part, you will need
Java Communications API. Its installation can be a little bit problematic. It is important to find a working tutorial for it. I dont remember which one i used so you need to find your way yourself. But you can start with installation instructions there.
2. Accessing a serial port on a remote machine
After you set up Java Communications API on the remote machine, you will need to develop a server application because you need to control a remote machine and to do this, you should have both client and server.
For client-server programming you can use socket programming or RMI (Remote Method Invocation). If you want to use a web based interface, then you can use Servlets to develop your server application and use your browser as the client application.
Let us know if you have further problems..