The WebSocket standard is almost finalized. However, WebSocket itself is offering “just” a (data) pipe. WebSocket is well suited to bring event- or data-driven applications to the browser. A valid example would a Web UI for a JMS or AMQP application. With help of the Kaazing Gateway this is possible! As said before, you are basically able to bring any TCP- or UDP-based application to the web.
A simple TCP-based echo server
Since the WebSocket client API itself is not enough (to build a “real” application), we need some (existing) backend, or server. A very simple example would be to bring a (TCP) echo server to the browser, via WebSocket:
var net = require('net');
var server = net.createServer(function (socket) {
// "on data" event listener:
socket.on('data', function(data) {
console.log('Got this data: ' + data)
// Echo:
socket.write('You said: ' + data);
});
});
server.listen(1337, '127.0.0.1');
The above code is a VERY simple “EchoServer” that runs on port “1337″. It is in Node.js. The code is borrowed from their website.
Bring it to the Web
To be able to access this TCP server with a WebSocket application you need to add the following configuration to the Kaazing WebSocket Gateway:
<service>
<accept>ws://localhost:8000/echo</accept>
<connect>tcp://localhost:1337/</connect>
<type>proxy</type>
<cross-site-constraint>
<allow-origin>*</allow-origin>
</cross-site-constraint>
</service>
The entry point for the echo server is the ws://localhost:8000/echoURL. The Gateway connects the WebSocket connection to the backend (check the tcp port). The connection to the echo server is straightforward. The following shows a pretty simple JavaScript program, that opens a WebSocket connection in order to send and receive data from the underlying TCP server:
var websocketConnection = new WebSocket("ws://localhost:8000/echo");
websocketConnection.onopen = function(ev) {
console.log('Connected to the echo service')
};
websocketConnection.onmessage = function(event) {
var payload = event.data;
displayEcho(payload);
};
...
websocketConnection.send("Hello Echo Server");
...
This is obviously a simple example, but it clearly shows the power of WebSocket! Give it a try!
If you are interested in HTML5 and WebSocket, check out the Kaazing Gateway! BTW. Kaazing is hiring…
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