ZStreamMUX
There's a maxim, a citation for which I can't locate now, which pours scorn on the idea of multiplexing streams over TCP. It kinda made sense when I first saw it, but in these days of ornery system adminstrators and their firewalls that sometimes allow connections seemingly on the roll of a die, there's a lot to be said for the all or nothing of getting a connection to a server, and then sharing it locally.
I wrote ZStreamMUX after coming across an early draft of WebMUX. ZStreamMUX takes a read stream and a write stream, and runs a lightweight protocol over them to support multiple independent sessions. The overall interface is similar to that provided by sockets. The protocol is asynchronous, and uses buffer credits to prevent deadlock at the protocol level.