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1. WebSockets-- Full-duplex Communication
The main HTML5 pillars include Markup, CSS3, and JavaScript APIs
For whole set of HTML5, visit html5rocks.com (Google product)
The URL
The following image shows the WebSocket URL example in tokens:
Schema Host Port Server
ws://example.com:8000/chat.php
WSS are supported as well and are the WebSocket equivalent to HTTPS for secure connections (SSL).
Who ' s using WebSockets
Name Website Description
Gamooga Http://www.gamooga.com/Real-time backend for apps and games
Gitlive http://gitlive.com/Notifications on GITHUB projects
Superfeedr Http://superfeedr.com/Real-time Data pushing
Pusher http://pusher.com/Scalable real-time functionality API for Web and mobile AP Ps
Smarkets Https://smarkets.com/Real-time Betting
IRC Cloud https://www.irccloud.com/Chatting
Great resources containing a large variety of WebSocket demos are as follows:
http://www.websocket.org/demos.html
http://www.html5rocks.com/en/features/connectivity
2. The WebSocket API Web Client
WebSocket communication and data transmission is bidirectional, so we need both parties to establish IT:A Ser Ver and a client.
HTML5 Basics:
For more information about the HTML5 markup, consider visiting http://html5doctor.com/. There is a complete reference for the supported HTML5 tags at http://html5doctor.com/element-index/.
Http://www.css3.info/is a great resource for CSS3 and further reading.
The markup defines the structure and the CSS rules apply the styling. What is about event handling and user actions? Well, here comes javascript! The WebSocket API is pure JavaScript, too!
WebSocket API allows connect to a local or remote server, listen for messages, send data, and CLO Se the connection. Typical WebSocket workflow shows below:
JavaScript provides an easy-to-find out whether a browser can execute websocket-specific code:
if (Window. WebSocket) { // validation check console.log ("WebSockets supported.") ); // Continue with the rest of the websockets-specific functionality ... }else {console.log ("WebSockets not supported.") ); Alert ("Consider updating your browser for a richer experience.") );}Want to see which browsers does support the WebSocket protocol? There is a up-to-date resource available at http://caniuse.com/#feat =websockets.
You can handle them either by implementing the OnOpen, OnMessage, OnClose, and onerror functions respectively, or by using The AddEventListener method.
Properties Description
URL Returns The URL of the WebSocket protocol Returns the protocol used by the server
ReadyState Reports The state of the connection and can take one of the following Selfexplanatory values:
Websocket.open
Websocket.closed
Websocket.connecting
Websocket.closing
Bufferedamount Returns The total number of bytes this were queued when the Send () method is called
Binarytype Returns The binary data format we
Received when the OnMessage event was raised
The Complete client example:
Index.html:
<!DOCTYPE HTML><HTML><Head><title>HTML5 WebSockets</title><Linkrel= "stylesheet"href= "Style.css" /><Scriptsrc= "Chat.js"></Script></Head><Body><H1>HTML5 WebSocket Chat.</H1><inputtype= "text"ID= "Text-view" /><inputtype= "button"ID= "Send-button"value= "send!" /><inputtype= "button"ID= "Stop-button"value= "Stop" /></BR><labelID= "Status-label">Status</label></Body></HTML>View Code
Chat.js:
1Window.onload =function() {2 varTextView = document.getElementById ("Text-view");3 varButtonsend = document.getElementById ("Send-button");4 varButtonstop = document.getElementById ("Stop-button");5 varLabel = document.getElementById ("Status-label");6 varSocket =NewWebSocket ("ws://echo.websocket.org");7Socket.onopen =function(event) {8label.innerhtml = "Connection Open";9 }TenSocket.onmessage =function(event) { One if(typeofEvent.data = = = "string") { Alabel.innerhtml = label.innerhtml + "<br/>" +Event.data; - } - } theSocket.onclose =function(event) { - varCode =Event.code; - varReason =Event.reason; - varWasclean =Event.wasclean; + if(Wasclean) { -label.innerhtml = "Connection closed normally."; + } A Else { atlabel.innerhtml = "Connection closed with message:" + -Reason + "(Code:" + code + ")"; - } - } -Socket.onerror =function(event) { -label.innerhtml = "Error:" +event; in } -Buttonsend.onclick =function() { to if(Socket.readystate = =websocket.open) { + socket.send (textview.value); - } the } *Buttonstop.onclick =function() { $ if(Socket.readystate = =websocket.open) {Panax Notoginseng socket.close (); - } the } +}View Code
Server side:
Server Client
Create a server on localhost:8181
Start Running
Initial Handshake:establish Connection <-----------Request connection
Handle the incoming message--------------------> Send message
Refer to Book (p.): http://www.amazon.com/getting-started-html5-websocket-programming/dp/1782166963
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