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Introduction

Using Java-Websocket is very similar to using javascript websockets: You simply take the client or the server class and override its abstract methods by putting your appilication logic in place.

These methods are

• onOpen
• onMessage
• onClose
• onError
• onStart (just for the server)

FAQ

If you have any questions, please check out the FAQ-page.

Server Example

import java.net.InetSocketAddress;

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

public class SimpleServer extends WebSocketServer {

	public SimpleServer(InetSocketAddress address) {
		super(address);
	}

	@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("new connection to " + conn.getRemoteSocketAddress());
	}

	@Override
	public void onClose(WebSocket conn, int code, String reason, boolean remote) {
		System.out.println("closed " + conn.getRemoteSocketAddress() + " with exit code " + code + " additional info: " + reason);
	}

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

	@Override
	public void onMessage( WebSocket conn, ByteBuffer message ) {
		System.out.println("received ByteBuffer from "	+ conn.getRemoteSocketAddress());
	}

	@Override
	public void onError(WebSocket conn, Exception ex) {
		System.err.println("an error occured on connection " + conn.getRemoteSocketAddress()  + ":" + ex);
	}
	
	@Override
	public void onStart() {
		System.out.println("server started successfully");
	}


	public static void main(String[] args) {
		String host = "localhost";
		int port = 8887;

		WebSocketServer server = new SimpleServer(new InetSocketAddress(host, port));
		server.run();
	}
}

Client Example

import java.net.URI;
import java.net.URISyntaxException;

import org.java_websocket.client.WebSocketClient;
import org.java_websocket.drafts.Draft;
import org.java_websocket.drafts.Draft_6455;
import org.java_websocket.handshake.ServerHandshake;

public class EmptyClient extends WebSocketClient {

	public EmptyClient(URI serverUri, Draft draft) {
		super(serverUri, draft);
	}

	public EmptyClient(URI serverURI) {
		super(serverURI);
	}

	@Override
	public void onOpen(ServerHandshake handshakedata) {
		send("Hello, it is me. Mario :)");
		System.out.println("new connection opened");
	}

	@Override
	public void onClose(int code, String reason, boolean remote) {
		System.out.println("closed with exit code " + code + " additional info: " + reason);
	}

	@Override
	public void onMessage(String message) {
		System.out.println("received message: " + message);
	}

	@Override
	public void onMessage(ByteBuffer message) {
		System.out.println("received ByteBuffer");
	}

	@Override
	public void onError(Exception ex) {
		System.err.println("an error occurred:" + ex);
	}

	public static void main(String[] args) throws URISyntaxException {		
		WebSocketClient client = new EmptyClient(new URI("ws://localhost:8887"));
		client.connect();
	}
}

To connect to a server with a normal signed certificate, you can do it this way as well!

ExampleClient c = new ExampleClient( new URI( "wss://echo.websocket.org" ) )

If you are using a self signed certificate, take a look at the SSLClientExample.java.

Additional Examples

You can find additional examples here.