+Structure
+=========
+
+Offset Size Type Description
+ 0 4 data protocol tag, must be 0xFB1AB1AF
+ 4 2 uint sequence number
+ 6 2 uint sequence ack
+ 8 4 data bitfield with previous acks
+12 1 uint type code for the payload
+13 3 none padding, reserved for future use
+16 0-484 data payload, contents and length vary,
+ mostly depending on the type code
+
+all multibyte values are in LE
+the current code does no conversion, so only works on machines
+with native LE (or BE if the server and all clients are on that,
+but that's by accident and will break if conversion code is ever
+added)
+
+