Tunneling A Protocol Through HTTP - Advice

Question

What are the best examples of real life protocols that tunnel through HTTP? XMPP/Jabber? I'm looking for actual links to documentation? or specs for how they tunnel.

I'm in working on project where I'm wondering if I should start with REST, XML-RPC, or SOAP and then have a fast TCP flavor of the protocol. Or start at the low level and then tunnel over HTTP using something more POX-like.

To start off with clients using this protocol will be written in Ruby, Java and .NET, and then possibly branch off into Python, Perl, Scala, Erlang, etc...

REQUIREMENTS:
1) Clients can attach to the server through the HTTP communication channel or straight TCP on another port. The TCP chatter would be streaming XML much-like jabber
2) I don't necessarily want to be XMPP compatible or write my own XMPP server.
3) The server will be written in 100% .NET (but Mono-friendly)
4) Clients could be written in anything (but see above - Ruby, Java, and .NET first)

Answer 1

The great thing about HTTP based protocols is how easy they are to test, and how many control features you get with the web/app servers that run them. It's awesome to just paste a query string to a colleague and have them take a look at your call and output. Also you don't have to deal with any of the connection setup and tear down code because (for instance) apache is already taking care of it for you. Plus you get all kinds of nifty meta info for free.