I (nobody ask me why) recently implemented a server-side IBB->TCP proxy. Everything went smoothly, and it actually maps quite nicely, given that it is already bidirectional.
One noticeable thing lacking though is a way to close a stream with an error. I can add this data in a new namespace, but it struck me that it might be useful to specify either a way to add an error to a <close/> stanza, or simply (but perhaps less cleanly, as it only works in direct reply to an incoming data packet) specify that a stream is closed if any type="error" stanza is received in reply to a sent stanza. Thoughts? Matthew PS. If anyone is interested, my proxy is documented here: http://code.google.com/p/prosody-modules/wiki/mod_tcpproxy and the code is in the repository at http://code.google.com/p/prosody-modules/source/browse/#hg/mod_tcpproxy (it includes a demo Javascript client).
