Serial communication - A simulator based on request msg from other device, it should send response.

Hi,

I want to create a simulator, which checks the request msg received from other devices via serial port and based on the request simulator should response msg.

For example: 

Other Device Request to my simulator : 2B 2B 2B

My Simulator  Response : 65 6E 74 72 61 4E 45 54 3E 20

Also, there are series of request message send sequentially to the simulator and after response is sent by simulator for each request - login successful.

Any heads up on how to proceed is highly appreciated.

Thanks