Your problem is in the use of unpack("B*", ...). The unpack there takes raw binary data and turn it into a human-readable string of 1s and 0s. The pack you are using already returns a raw data that is probably suitable for sending over the socket. (agh! see update below.)

You should probably be using syswrite or you should turn off buffering.

update: Oops, mental error, the pack format's wrong. See node below.