To test the program, first compile server.cpp and backdoor.cpp, then open 1 terminal window to run the server and 1 to run the backdoor.
Run the server first; the server will run on localhost (127.0.0.1) and will listen on port 5400 and accept any IP address.
Then run the backdoor, the backdoor will connect to the server and you will be able to send commands from the server terminal to the backdoor terminal.