WebSocket Learning

Use Java-WebSocket to implement a simple chat server.

Java codes:

import org.java_websocket.WebSocket;
import org.java_websocket.handshake.ClientHandshake;
import org.java_websocket.server.WebSocketServer;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;

/**
 * A simple WebSocketServer implementation. Keeps track of a "chatroom".
 */
public class ChatServer extends WebSocketServer {

    public ChatServer(int port) {
        super(new InetSocketAddress(port));
    }

    @Override
    public void onOpen(WebSocket conn, ClientHandshake handshake) {
        conn.send("Welcome to the server!"); // This method sends a message to the new client
        broadcast("new connection: " + handshake.getResourceDescriptor()); // This method sends a message to all clients connected
        System.out.println(conn.getRemoteSocketAddress().getAddress().getHostAddress() + " entered the room!");
    }

    @Override
    public void onClose(WebSocket conn, int code, String reason, boolean remote) {
        broadcast(conn + " has left the room!");
        System.out.println(conn + " has left the room!");
    }

    @Override
    public void onMessage(WebSocket conn, String message) {
        broadcast(message);
        System.out.println(conn + ": " + message);
    }

    @Override
    public void onError(WebSocket conn, Exception ex) {
        ex.printStackTrace();
        if (conn != null) {
            // some errors like port binding failed may not be assignable to a specific websocket
        }
    }

    @Override
    public void onMessage(WebSocket conn, ByteBuffer message) {
        broadcast(message.array());
        System.out.println(conn + ": " + message);
    }

    public static void main(String[] args) throws InterruptedException, IOException {
        ChatServer s = new ChatServer(8887);
        s.start();

        BufferedReader sysin = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String in = sysin.readLine();
            s.broadcast(in);
            if (in.equals("exit")) {
                s.stop(1000);
                break;
            }
        }
    }

    @Override
    public void onStart() {
        System.out.println("Server started!");
        setConnectionLostTimeout(0);
        setConnectionLostTimeout(100);
    }
}

JavaScript codes:

ws = new WebSocket("ws://localhost:8887");

ws.onopen = function () {
    ws.send('hello from client')
};

ws.onmessage = function (evt) {
    var msg = evt.data
    console.log(`received msg is ${msg}`)
}

ws.onclose = function () {
    console.log("closed")
}

Run the code above in browser's snippets window.

Then run the code below in the console window.

ws.send('hello')
ws.send('world')
ws.send('8623')