has session tags within it, send an additional ping to the peer,
bundling those tags a second time, ACKing those tags on the pong.
* handle packets transferred during a race after the receiver ACKs the
connection but before the establisher receives the ACK.
* notify the messageInputStream reader on close (duh)
* new stream sink test, shoving lots and lots of data down a stream
with the existing StreamSinkServer and StreamSinkClient apps
* logging