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Introducing WebSockets: Bringing Sockets to the Web

Introducing WebSockets: Bringing Sockets to the Web
The Problem: Low Latency Client-Server and Server-Client Connections The web has been largely built around the so-called request/response paradigm of HTTP. A client loads up a web page and then nothing happens until the user clicks onto the next page. Around 2005, AJAX started to make the web feel more dynamic. Still, all HTTP communication was steered by the client, which required user interaction or periodic polling to load new data from the server. However, all of these work-arounds share one problem: They carry the overhead of HTTP, which doesn't make them well suited for low latency applications. Introducing WebSocket: Bringing Sockets to the Web The WebSocket specification defines an API establishing "socket" connections between a web browser and a server. Getting Started You open up a WebSocket connection simply by calling the WebSocket constructor: var connection = new WebSocket(' ['soap', 'xmpp']); Notice the ws:. Communicating with the Server

Comet (programming) Comet is a web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it.[1][2] Comet is an umbrella term, encompassing multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins. The Comet approach differs from the original model of the web, in which a browser requests a complete web page at a time.[3] The use of Comet techniques in web development predates the use of the word Comet as a neologism for the collective techniques. The ability to embed Java applets into browsers (starting with Netscape 2.0 in March 1996[10]) made real-time communications possible, using a raw TCP socket[11] to communicate between the browser and the server. Even if not yet known by that name, the very first Comet implementations date back to 2000,[18] with the Pushlets, Lightstreamer, and KnowNow projects.

buildar/getting_started_with_webrtc How to write a Long Polling Event Push Server with node.js – go-left Software Quick jumps: The API – Installing node – The Skeleton – POSTing Events – GETting Events – Pausing and Resuming Requests – Final Disclaimer For one of my JavaScript projects I’ve needed a push technology to push server events to my web clients. After looking at several options I’ve decided to write a long polling server with node.js. I am going to explain step by step how I’ve done that. Feedback is welcome. The sample code is available on gist.github git clone The long polling server performs only the task of pushing server events to the client. To make the server more useful we assume that a user can connect simultaneously with multiple browsers and an event pushed for that user is pushed to all browsers the user is currently using (one producer, many consumers). We further want the client/server communication to be robust therefore we don’t know anything about the state of the client and leave it up to the client to request the events it wants to see.

A Web RTC Tutorial With WebRTC, adding a peer-to-peer video chat to a site is as easy as child's play and the best part of it is that there is no need for your users to download plugins to use the service. There are two pieces needed to set up peer-to-peer video chat using WebRTC: an HTML5 compliant browser, and the proper code on your server. This blog will walk you through the steps to get a simple service up and running. WebRTC is part of the HTML5 standard and is still under development. But by downloading an augmented WebKit library from Ericsson Labs, you can try it out today. At present, only Ubuntu 11.04 is supported for the browser, but there are no such restrictions on the server. Installing the Browser To install the browser, follow the steps here. /usr/lib/webkitgtk-1.0-0/libexec/GtkLauncher Note that the following steps are only required if you want to host the signaling server yourself. Setting up the Server Then, install libevent: before the install step: <! Step 1

WebSockets is cool, but what can you do today? | Clay Lenhart’s Blog WebSockets is a new feature that appears to be a great way to send messages from the server to the browser, however today there isn’t much support, both in browsers and on the server in IIS and ASP.Net. Today you can use a Comet technique (in particular, Ajax with long polling ) which is available in all browsers. Using this concept, the browser makes a standard AJAX call to the server that waits until it receives a message. Asynchronous Pages and Asynchronous Controller allow you to have long running HTTP requests without using precious ASP.Net threads. On the server, there are two resource limits to consider with IIS and ASP.Net: HTTP request limits — in IIS7 the default limit is 5000 ASP.Net thread limits — in IIS7 the default limit is 12 x number of CPUs For a typical ASP.Net application (and ASP.Net MVC application), an HTTP request always uses an ASP.Net thread. Take for example an email web application that has jQuery code to check for new mail. $( function () { checkEmail(); } else {

Getting Started with WebRTC WebRTC is a new front in the long war for an open and unencumbered web. Brendan Eich, inventor of JavaScript Real-time communication without plugins Imagine a world where your phone, TV and computer could all communicate on a common platform. Imagine it was easy to add video chat and peer-to-peer data sharing to your web application. That's the vision of WebRTC. Want to try it out? Open apprtc.appspot.com in Chrome, Opera or Firefox. There is a walkthrough of this application later in this article. Quick start Haven't got time to read this article, or just want code? Get an overview of WebRTC from the Google I/O presentation (the slides are here): If you haven't used getUserMedia, take a look at the HTML5 Rocks article on the subject, and view the source for the simple example at simpl.info/gum. Alternatively, jump straight into our WebRTC codelab: a step-by-step guide that explains how to build a complete video chat app, including a simple signaling server. A very short history of WebRTC

Stream Updates with Server-Sent Events Introduction I wouldn't be surprised if you've stumbled on this article wondering, "What the heck are Server-Sent Events (SSEs)?" Many people have never heard of them, and rightfully so. Over the years, the specification has seen significant changes, and the API has taken somewhat of a backseat to newer, sexier communication protocols such as the WebSocket API. Polling is a traditional technique used by the vast majority of AJAX applications. Long polling (Hanging GET / COMET) is a slight variation on polling. Server-Sent Events on the other hand, have been designed from the ground up to be efficient. The main difference between Server-Sent Events and long-polling is that SSEs are handled directly by the browser and the user simply has to listen for messages. Server-Sent Events vs. Why would you choose Server-Sent Events over WebSockets? SSEs are sent over traditional HTTP. JavaScript API To subscribe to an event stream, create an EventSource object and pass it the URL of your stream: <!

WebRTC in the real world: STUN, TURN and signaling What is signaling? Signaling is the process of coordinating communication. In order for a WebRTC application to set up a 'call', its clients need to exchange information: Session control messages used to open or close communication.Error messages.Media metadata such as codecs and codec settings, bandwidth and media types.Key data, used to establish secure connections.Network data, such as a host's IP address and port as seen by the outside world. This signaling process needs a way for clients to pass messages back and forth. Why is signaling not defined by WebRTC? To avoid redundancy and to maximize compatibility with established technologies, signaling methods and protocols are not specified by WebRTC standards. JSEP's architecture also avoids a browser having to save state: that is, to function as a signaling state machine. JSEP requires the exchange between peers of offer and answer: the media metadata mentioned above. Want to know what all this SDP gobbledygook actually means? <!

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