How does Gmail do comet on Opera?

Question

I would like to know how Gmail (or anyone else) does comet on Opera.

Here is what I know so far from my experiments.

1. It doesn\'t use the event-source tag w

Answer 1

I am the author of an in progess C++ HTTP server that is compatible with goog.netBrowserChannel. You can find the docs I've written while studying the protocol here:

http://code.google.com/p/libevent-browserchannel-server/wiki/BrowserChannelProtocol

Long story short, BrowserChannel uses forever frames on IE and XHR streaming on all other browsers. The protocol is divided into several phases, the first of which is network testing:

1) test the network to ensure response "streaming" is supported (in other words no buffering proxy exists)
2) check access to a variety of network prefixes (to make sure the network admin has not blocked access to chat)

Then the actual data transmission can start. Data is divided into two channels (forward and back). The back channel is a series of long lived (about 4 mins each) requests used for the server to "stream" content to the client. To do so HTTP chunked encoding is used. The client does it's best to make sure that one backchannel is always open. The server will close it about every 4 mins after which the client will open a new backchannel. The forward channel is used to send data from the client to the server. This pushing of data is done as necessary.