[LINK] WebSockets

Roger Clarke Roger.Clarke at xamax.com.au
Tue Mar 29 12:46:38 AEDT 2011

>On 29/03/2011, at 11:52 AM, Paul Bolger wrote:
>>  So how is this different for the end user to the AJAX, or whatever it
>>  is, that Ebay uses to drive the real time bid price updates?

At 12:24 +1100 29/3/11, Ivan Trundle wrote:
>AJAX clients just send requests (post or get typically) to the 
>server and await a response - there is an overhead when multiple 
>requests are queued. AJAX works through the XMLHttpRequest object in 
>the DOM API. Each AJAX request opens a new connection between 
>browser and server.
>Websockets is an alternative API, from my understanding (a type of 
>push technology), which allows more control over the socket that the 
>browser creates, and allows for non-http transfers (such as 
>streaming), and bi-directional transfers. It also reduces the 
>overhead at either end, since the connection between client and 
>server stays open. Useful for asynchronous data transmission.

I'd have thought that a keep-open / long-TTL on the TCP session would 
be adequate to overcome (a lot of) those overheads.  But if I'm wrong 
I'd be pleased to have a quick tut or a pointer to an explanation 

And TCP sessions aren't limited to HTTP.

So it seems to me that there are other motivations underlying Websockets.

Roger Clarke                                 http://www.rogerclarke.com/

Xamax Consultancy Pty Ltd      78 Sidaway St, Chapman ACT 2611 AUSTRALIA
                    Tel: +61 2 6288 1472, and 6288 6916
mailto:Roger.Clarke at xamax.com.au                http://www.xamax.com.au/

Visiting Professor in the Cyberspace Law & Policy Centre      Uni of NSW
Visiting Professor in Computer Science    Australian National University

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