Threaded Java socket server and client

Create a server at port 5556 with a MessageHandler, which is the EchoHandler in this example.

SocketServer server = new SocketServer(5556, new EchoHandler());

Create a client connecting to localhost's port 5556.

SocketClient client = new SocketClient(InetAddress.getLocalHost(), 5556);

Send a message from the client.

client.println("Hello!");

Print out the message from the server. The function SocketClient.readLine() blocks.

System.out.println(client.readLine());

The EchoHandler implements the MessageHandler interface and overrides the abstract method onReceive(). The argument connection enables you to send a string back to the client.

public class EchoHandler implements MessageHandler {
    @Override
    public void onReceive(Connection connection, String message) {
        connection.send(message);
    }
}

SocketServer is threaded. It creates a thread for accepting connections and creates a new thread each time a new client is connected. SocketClient is not threaded and the function readLine() blocks.