CODEWITHSUNDEEP
javascriptajax
pimvdb
pimvdb

Reputation: 154828

Checking for updates using AJAX - bandwidth optimization possibilities?

I'm creating a simple online multiplayer game, with which two players (clients) can play the game with each other. The data is sent to and fetched from a server, which manages all data concerning this.

The problem I'm facing is how to fetch updates from the server efficiently. The data is fetched using AJAX: every 5 seconds, data is fetched from the server to check for updates. This is however done using HTTP, which means all headers are sent each time as well. The data itself is kept to an absolute minimum.

I was wondering if anyone would have tips on how to save bandwidth in this server/client scenario. Would it be possible to fetch using a custom protocol or something like that, to prevent all headers (like 'Server: Apache') being sent each single time? I basically only need the very data (only 9 bytes) and not all headers (which are like 100 bytes if it's not more).

Thanks.

Upvotes: 1

Views: 934

Answers (3)

Day
Day

Reputation: 9693

Comet or Websockets

HTML5's websockets (as mentioned in other answers here) may have limited browser support at the moment, but using long-lived HTTP connections to push data (aka Comet) gives you similar "streaming" functionality in a way that even IE6 can cope with. Comet is rather tricky to implement though, as it is kind of a hack taking advantage of the way browsers just happened to be implemented at the time.

Also note that both techniques will require your server to handle a lot more simultaneous connections than it's used to, which can be a problem even if they're idle most of the time. This is sometimes referred to as the C10K problem.

This article has some discussion of websockets vs comet.

Reducing header size

You may have some success reducing the HTTP headers to the minimum required to save bytes. But you will need to keep Date as this is not optional according to the spec (RFC 2616). You will probably also need Content-Length to tell browser the size of the body, but might be able to drop this and close the connection after sending the body bytes but this would prevent the browser from taking advantage of HTTP/1.1 persistent connections.

Note that the Server header is not required, but Apache doesn't let you remove it completely - the ServerTokens directive controls this, and the shortest setting results in Server: Apache as you already have. I don't think other webservers usually let you drop the Server header either, but if you're on a shared host you're probably stuck with Apache as configured by your provider.

Upvotes: 3

Art
Art

Reputation: 5924

This isn't possible for all browsers, but it is supported in newer ones(Chrome, Safari). You should use a framework that uses websockets and then gracefully degrades to long polling(you don't want to poll at fixed intervals unless there are always events waiting). This way you will get the benefit of the newer browsers and that pool will continue to expand as people upgrade.

For Java the common solution is Atmosphere: http://atmosphere.java.net. It has a jQuery plugin as well as a abstraction the servlet container level.

Upvotes: 1

hvgotcodes
hvgotcodes

Reputation: 120188

html5 sockets will be the way to do this in the near future.

http://net.tutsplus.com/tutorials/javascript-ajax/start-using-html5-websockets-today/

Upvotes: 1

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