javac Server.java

java Server

javac Client.java

java Client

Here the first input is the username you want to register with, second input the server's IP address and the third is the mode in which you want to the client application. It is recommended to run all client applications in the same mode.

Mode can take values 0, 1 or 2

in mode 0, there is no encryption and no signature

in mode 1, there is encryption but no signature

in mode 2, there is encryption and signature

The clients can send messages in the following format

@[recipient name] [message]