尝试访问WebSocket时收到错误404

Question

I am trying to set a simple example for a web socket in my site but I have no luck despite I reviewed a lot of similar cases and tutorials.

This is my config at server

java version "1.8.0_191"
Server version: Apache Tomcat/7.0.52 (Ubuntu)

And I use Netbeans at local.

Server side

This is my class. I am not registering anything at web.xml.

package com.myserver.server.monitor;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint(value = "/wss")
public class MonitorWebSocket { 

    private static Set<Session> peers = Collections.synchronizedSet(new HashSet<Session>());

    @OnOpen
    public void onOpen (Session peer) {
        peers.add(peer);
    }

    @OnClose
    public void onClose (Session peer) {
        peers.remove(peer);
    }

    @OnMessage
    public String mensaje(String mensaje) { 
        return "Hi, from server. The message was:" +mensaje;
    }

    @OnError
    public void onError(Throwable t) {
    }
}

Client side:

Before you point it, I think the URI is ok, as the context is ROOT.

I am typing 'wss' as it is a htpps site, and I get a coherent security exception if I use 'ws'

function initPerformance(){

    var uriWS="wss://myserver.com/wss";
    var miWebsocket= new WebSocket(uriWS);
    console.log (miWebsocket);

    miWebsocket.onopen=function(evento) {
        console.log("open");
        miWebsocket.send("hi");
    };

    miWebsocket.onmessage=function(evento) {
        console.log(evento.data);
    };
}

Results

in chrome console (similar results on FF):

performance.js:4 WebSocket connection to 'wss://myserver.com/wss' failed: Error during WebSocket handshake: Unexpected response code: 404

I wonder if some miss match on libraries between my development environment and server could be the reason, but catalina.out is not complaining about any import.

Placing ' https://myserver.com/wss ' on browser's bar also gives a 404 error

Any help will be appreciated.

Edit:

I found this valuable resource:

wss://echo.websocket.org

which I could try to call from client side. As I expected it works, so my problem is probably on server side.

Answer 1

Not sure what my therapist will think about talking alone here, but the thing is I came to a solution. Nothing in the above path worked and seems is not a good way for Tomcat7. I try before to implement it with a WebSocketServlet that seems to be the good old way for Tomcat7. But I had problems finding the correct libraries. At the end this is working for me:

Libraries (JAR files)

This one lets me invoke the 'old stuff' for 'WebSocketServlet' and other related classes.
I was not done, as everything seemed ok to compile in netbeans, but this error occurred:

class file for org.apache.coyote.http11.upgrade.UpgradeInbound not found

But this jar got rid of it ( as described here ).

Server side

Restructuring the code, I have two classes:

A Servlet like this:

package com.myserver.server.monitor;

import java.util.concurrent.ConcurrentHashMap;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.catalina.websocket.StreamInbound;
import org.apache.catalina.websocket.WebSocketServlet;

@WebServlet("/wsocket")
public class MonitorServlet extends WebSocketServlet {


    private static final long serialVersionUID = 1L;

    // for new clients, <sessionId, streamInBound>
    private static ConcurrentHashMap<String, StreamInbound> clients = new ConcurrentHashMap<String, StreamInbound>();

    @Override
    public void init(){

    }

    @Override
    protected StreamInbound createWebSocketInbound(String protocol,HttpServletRequest httpServletRequest) {

        // Check if exists
        HttpSession session = httpServletRequest.getSession();
        // find client
        StreamInbound client = clients.get(session.getId());
        if (null != client) {
            return client;
        } else {
            client = new MyInBound(httpServletRequest,this);
            clients.put(session.getId(), client);
        }

        return client;
    }

}

And the class MyInBound, like this:

package com.myserver.server.monitor;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import javax.servlet.http.HttpServletRequest;
import org.apache.catalina.websocket.MessageInbound;
import org.apache.catalina.websocket.WebSocketServlet;
import org.apache.catalina.websocket.WsOutbound;

public class MyInBound extends MessageInbound{

    //private String name;
    private WsOutbound myoutbound;
    private final WebSocketServlet servlet;

    public MyInBound(HttpServletRequest httpServletRequest, WebSocketServlet servlet) {
        this.servlet=servlet;
    }

    @Override
    public void onOpen(WsOutbound outbound) {
        this.myoutbound = outbound;
        System.out.println("Hey!!---------");
    }

    @Override
    public void onClose(int status) {
        System.out.println("Close client");
    }

    @Override
    protected void onBinaryMessage(ByteBuffer arg0) throws IOException {

    }

    @Override
    protected void onTextMessage(CharBuffer inChar) throws IOException {

    }

}

Now you should register the servlet in web.xml:

<servlet>
        <servlet-name>MonitorServlet</servlet-name>
        <servlet-class>com.myserver.server.monitor.MonitorServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>MonitorServlet</servlet-name>
        <url-pattern>/MonitorServlet</url-pattern>
    </servlet-mapping>

Client side

It didn't change very much:

function initPerformance(){

var uriWS="wss://myserver.com/wsocket";
var miWebsocket= new WebSocket(uriWS);
console.log (miWebsocket);

miWebsocket.onopen=function(evento) {
    console.log("open");
    miWebsocket.send("hi");
};

miWebsocket.onmessage=function(evento) {
    console.log(evento.data);
};

}

Hope it helps someone!