HTML 5 - Web Sockets
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This document discusses web sockets and how they provide for bi-directional, full-duplex communications over a single TCP connection. It describes how web sockets establish a connection using a handshake process and then allow text and binary frames to be sent back and forth between client and server with low overhead framing. The HTML5 web socket API is demonstrated for opening a connection and listening for messages and connection events.
HTML 5 - Web Sockets
- 1. Web Sockets Eyal Vardi CEO E4D Solutions LTD Microsoft MVP Visual C# blog: www.eVardi.com
- 2. Agenda Type of Communications Web Sockets API’s © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 3. Type of Communications © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 4. Periodic polling Polling interval Poll from time to time using Ajax Delay in communications due to polling interval Wastes bandwidth & latency © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 5. Long polling Poll but don’t respond untill there’s data Poll again after data received or after the connection times out Consumes server threads & connection resources © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 6. Forever Frame HTTP/1.1 200 OK Content-Type: text/plain Transfer-Encoding: chunked <script>eval("... ")</script>0 <script>eval("... ")</script>0 Server tells client that response is chuncked Client keeps connection open untill server closes it Server pushes data to the client followed by 0 Consumes server threads © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 7. WebSockets © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 8. What is WebSockets? WebSocket is a web technology providing for bi-directional, full-duplex communications channels over a single TCP connection. the communications are done over the regular TCP port number 80 or 443. ws:// and wss:// prefix to indicate a WebSocket and a WebSocket Secure connection, respectively. © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 9. WebSocket Protocol Handshake To establish a WebSocket connection, the client sends a WebSocket handshake request, and the server sends a WebSocket handshake response. GET /mychat HTTP/1.1 Client Host: server.example.com Upgrade: websocket Connection: Upgrade Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw== Sec-WebSocket-Protocol: chat Sec-WebSocket-Version: 13 Origin: http://example.com HTTP/1.1 101 Switching Protocols Server Upgrade: websocket Connection: Upgrade Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk= Sec-WebSocket-Protocol: chat © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 10. WebSocket Protocol Handshake WebSocket data frames can be sent back and forth between the client and the server in full- duplex mode. Both text and binary frames can be sent in either direction at the same time. The data is minimally framed with just two bytes. In the case of text frames, each frame starts with a 0x00 byte, ends with a 0xFF byte, and contains UTF-8 data in between. WebSocket text frames use a terminator, while binary frames use a length prefix. © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 11. HTML5 WebSocket API var myWebSocket = new WebSocket("ws://www.websockets.org"); myWebSocket.onopen = function(evt) { alert("Connection open ..."); }; myWebSocket.onmessage = function(evt) { alert("Received Message: " + evt.data); }; myWebSocket.onclose = function(evt) { alert("Connection closed."); } myWebSocket.send("Hello WebSockets!"); myWebSocket.close(); © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]
- 12. Web Socket Echo (http://www.websocket.org/echo.html) © 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: [email protected]