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IT Camp 2011

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Duplex Communications with WCF and Azure

Florin Cardașim, software developerRomSoft Iași, www.rms.ro

caf@rms.ro | twitter.com/cardasim

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Session agenda

• Enterprise duplex. Non-browser clients–WCF duplex bindings, router service–Windows Azure Service Bus

• Web duplex. Browser clients– Simple polling, comet/long polling–WebSockets

• Q&A

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ENTERPRISE DUPLEX

Non-browser clients- WCF duplex bindings, router service- Windows Azure Service Bus

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Full duplex using WCF NetTcpBinding

Event consumer

Event publisher

Publisher requires public IPCustom ports open in firewall

Full duplex TCP

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“Full duplex” using WCF WSDualHttpBinding

Event consumer

Event publisher

Network address translation makes connection back

impossible

Duplex HTTPNAT

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“Full duplex” using WCF WSHttpBinding

Event consumer

Event publisher

Publisher and consumers require public IPThat’s fine, BUT we want the servers INSIDE the enterprise

Dual HTTP

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WCF Router Service

Event consumer

Event publisher

Firewall and NAT friendlyRouters have protocol bridging, failover etcNot bad, but quite crowded. Can you do better?

Dual HTTP TCPTCP

Router Service Router Service

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Windows Azure Service Bus

Eventconsumer

Event publisher

Relay Service

sb://itcampnamespace.servicebus.windows.net/publisher

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DEMO

Connecting the enterprises via:-NetTcpBinding, WsDualHttpBinding-RouterService, NetTcpBinding, WsDualHttpBinding-Service Bus, NetEventRelayBinding

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Enterprise duplex: conclusions

• Direct TCP is best IF available• public endpoint , open ports in firewall

• Duplex HTTP is an alternative• public IP both publisher and consumer, port 80

• Router Service bridges the enterprises• flexible, but quite complicated deployment

• Azure Service Bus• very flexible & powerful; requires careful

planning because each connection costs money

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WEB DUPLEX

Browser clients- Simple polling, comet/long polling- WebSockets

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Http polling

• Wasted resources, many requests return no data

• Frequent polling means higher load on the server

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Comet/long polling

• Bandwidth: small payload, large http headers overhead

• Scalability: pressure on memory, bandwidth, threads/processes

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DEMO

An open source, WCF based, long polling server implementation:http://laharsub.codeplex.com/

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Html5 WebSockets

• Full duplex, bidirectional• Single TCP socket• Standard ports: http/80,

https/443• Bandwidth savings• More scalable than Comet• Nice programming model• In&outside of browser

Open WebSocket Connection

Server

Client

Drafts:-IETF WebSockets Protocol-W3C WebSockets API

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Html5/websockets: server

• Socket.IO (Java, node.js)

• Jetty (Java)• Ruby/EventMachine• Python/Twisted• WCF websocket

prototype • … others

• Socket.IO Fallbacks– Adobe Flash Socket– AJAX Long Polling– AJAX Multipart

Streaming– Forever iFrame– JSONP Polling

• http://socket.io/

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Html5/websockets: server

• Test browser support: http://websocket.org/echo.html

• Microsoft is still experimenting

• http://html5labs.com

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DEMO

Some WebSockets in action:http://kaazing.mehttp://retrospectiveapp.heroku.com

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DEMO

Using the WCF WebSockets prototype from http://html5labs.com

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References

• channel9.msdn.com/Learn/Courses/Azure/ServiceBus

• en.wikipedia.org/wiki/Comet_%28programming%29

• html5rocks.com/tutorials/websockets/basics• websocket.org• pusher.com• kaazing.com• live.visitmix.com/MIX11?q=web+sockets• paulbatum.com

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Q&A

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