Javascript client can't connect to java server

Question

I am working on a simple server, just to learn how it works. I got a java server and java client to work, but trying to get a javascript client to connect to the same java server is driving me crazy!

Java server:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class DateServer {

    public static void main(String[] args) throws IOException {
        ServerSocket listener = new ServerSocket(9091);
        System.out.println("Starting");
        try {
            while (true) {
                System.out.println("While");
                Socket socket = listener.accept();
                System.out.println("Accepted");
                BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String msg = input.readLine();
                System.out.println("Message from client: " + msg);
                try {
                    PrintWriter out =
                        new PrintWriter(socket.getOutputStream(), true);

                    System.out.println("Sending message...");
                    out.println("Hi");
                } finally {
                    System.out.println("Closing socket");
                    socket.close();
                }
            }
        }
        finally {
            listener.close();
        }
    }
}

Java client: (which works)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

import javax.swing.JOptionPane;

public class DateClient {

    public static void main(String[] args) throws IOException {
        Socket s = new Socket("localhost", 9091);

        try {
            PrintWriter out =
                new PrintWriter(s.getOutputStream(), true);

            System.out.println("Sending message...");
            out.println("I'm the client");
        } finally {
            //System.out.println("Closing socket");
            //s.close();
        }

        BufferedReader input = new BufferedReader(new InputStreamReader(s.getInputStream()));
        String msg = input.readLine();
        System.out.println(msg);
        JOptionPane.showMessageDialog(null, msg);
        s.close();
        System.exit(0);
    }
}

JavaScript client:

<!DOCTYPE html>

<html>
<head>
        <title>Echo Test</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width">
    </head>
<body>
<div id="messages"></div>
<script type="text/javascript">

var connection = new WebSocket('ws://localhost:9091/');
var messages = document.getElementById("messages");

// When the connection is open, send some data to the server
connection.onopen = function (e) {
  writeResponse('sent');
  connection.send('Ping');
}

// Log errors
connection.onerror = function (error) {
  writeResponse('Error: ' + error);
}

connection.onclose = function(e){
    writeResponse("Disconnected: " + e.data);
}

// Log messages from the server
connection.onmessage = function (e) {
  writeResponse('Server: ' + e.data);
}

function writeResponse(text){
                messages.innerHTML += "<br/>" + text;
            }

</script>
</body>
</html>

When I run the java client with the server I get:

Starting
While
Accepted
Message from client: I'm the client
Sending message...
Closing socket
While

and output from the client:

Sending message...
Hi

So that works. When I run the javascript client, the server's output is:

Starting
While
Accepted
Message from client: GET / HTTP/1.1
Sending message...
Closing socket
While

And the output on the javascript page is:

Error: [object Event]
Disconnected: undefined

Also, firefox console says "Firefox can't establish a connection to the server at ws://localhost:9091/". What am I missing? Thanks!

Answer 1

A webSocket connection from a browser is not just a plain TCP connection. It MUST support the full webSocket protocol or the browser will not be able to connect to it or exchange data. This full webSocket protocol includes:

An initial connection via HTTP
An upgrade to the webSocket protocol
The security procedure for initializing a webSocket connection
The webSocket data packet format

You can read more about that here: https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API/Writing_WebSocket_servers

Javascript client can't connect to java server

Question

1 answers

solution1
1 ACCPTED 2016-03-21 06:46:27

Javascript client can't connect to java server

Question

1 answers

solution1 1 ACCPTED 2016-03-21 06:46:27

solution1
1 ACCPTED 2016-03-21 06:46:27