yes, i think this would work. unfortunately, i can't see anything in "pure" javascript that is equivalent: the xmlhttprequest is restricted to the originating

yes, i think this would work. unfortunately, i can't see anything in "pure" javascript that is equivalent: the xmlhttprequest is restricted to the originating ip (and it looks like they are single request/response, but in practice perhaps that could be worked around); websockets have the same restriction (but are bi-directional and multiple message) plus they are implemented on top/inside of the http stream, so don't (uniquely) own a tcp connection. and server-side java libs exist for hole punching. so you could pretty easily implement a java-only solution, called from javascript.