One of the questions I brought up on a previous blog – Comet servers for a Single-Dealer Platform – was that of bandwidth. The main thing that affects bandwidth that a Comet server has some control over is message size. At the time of that blog I hadn’t looked into this issue with all the servers in much detail, so I decided to dive a little deeper and look at the protocols of some of the Comet servers written about on that blog.
A question that a customer once asked was about message sizes, but the question was wrong, they asked what performance Liberator could handle with 1K messages – they wanted to compare Liberator to another Comet server sending 1K messages. I pointed out that they should let us know what the payload they want to send is and we can see the size of the message in our protocol, and they should do the same with the other Comet server. Maybe we could represent a much bigger payload in a 1K message than the other server could.
I have looked at four servers for this blog – Liberator, Lightstreamer, Adobe LCDS and my-Channels Nirvana. They all take slightly different approaches, but can all be used to achieve similar results. My test case is a single message payload, but I am showing the structure of the messages and will comment on how different payloads may be represented better or worse in the different servers.
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