Simple Websocket Client in Java - Connection issue

Question

I'm trying to write a simple websocket client in Java to connect to a 3rd party WebSocket server (I have no access to the server).

I can connect and communicate with the websocket server using javascript in a browser, but when I try and do the same thing using a Java client it fails to connect.

With the same java client I can connect to a tomcat websocket server I have running, so I think it's some sort of compatibility issue between the client and server. (I'm using Tomcat 7.0.56 libraries for the websocket client).

This is the error I get...

Error

javax.websocket.DeploymentException: The HTTP request to initiate the WebSocket connection failed
    at org.apache.tomcat.websocket.WsWebSocketContainer.connectToServer(WsWebSocketContainer.java:344)
    at org.apache.tomcat.websocket.WsWebSocketContainer.connectToServer(WsWebSocketContainer.java:166)
    at com.cvr.instant.ws.WebSocketClient.Connect(WebSocketClient.java:44)
    at com.cvr.instant.ws.TestWS.Start(TestWS.java:17)
    at com.cvr.instant.ws.TestWS.main(TestWS.java:37)
Caused by: java.io.EOFException
    at org.apache.tomcat.websocket.WsWebSocketContainer.processResponse(WsWebSocketContainer.java:595)
    at org.apache.tomcat.websocket.WsWebSocketContainer.connectToServer(WsWebSocketContainer.java:317)
... 4 more

WebSocketClient

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

import javax.websocket.ClientEndpoint;
import javax.websocket.CloseReason;
import javax.websocket.ContainerProvider;
import javax.websocket.DeploymentException;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;

@ClientEndpoint
public class WebSocketClient {

    protected   WebSocketContainer container;
    protected   Session userSession = null;

    public WebSocketClient() {
        container = ContainerProvider.getWebSocketContainer();
    }

    public void Connect(String sServer) {

          try {
              userSession = container.connectToServer(this, new URI(sServer));

            } catch (DeploymentException | URISyntaxException | IOException e) {
                e.printStackTrace();
            }

    }

    public void SendMessage(String sMsg) throws IOException {
        userSession.getBasicRemote().sendText(sMsg);
    }

    @OnOpen
    public void onOpen(Session session) {
        System.out.println("Connected");
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
    }

    @OnMessage
    public void onMessage(Session session, String msg) {
        System.out.println(msg);
    }

    public void Disconnect() throws IOException {
        userSession.close();
    }
}

Running the client

import java.io.IOException;

public class TestWS {

    public WebSocketClient wsc;
    public TestWS() {
    }

    public void Start() throws InterruptedException, IOException {

        wsc = new WebSocketClient();
        wsc.callback = this;
        wsc.Connect("ws://192.168.0.25:9000");
        Thread.sleep(1000);
        wsc.Disconnect();
    }


    public static void main(String[] args) throws InterruptedException, IOException 
    {
        TestWS t = new TestWS();
        t.Start();
        Thread.sleep(1000);
    }

}    

I'm very new to websocket clients (and fairly new to websockets in general). Any help you can give would be appreciated!

Answer 1

I found the issue - it was that the ws address required a '/' on the end of it when being run from a java client.

JavaScript ws://192.168.0.25:9000

Java ws://192.168.0.25:9000/

Not sure why this is required in Java - but it solved the issue...