ONLY WAY OF DATA TRANSFER:
CLIENT --> SERVER

PASSWORD_HASH is in md5
Structure:

(USERNAME,PASSWORD_HASH,ACTION,DATA)

ACTION == ("START" | "TRANSMIT" | "STOP")

DATA == ("" | POSITION, TIME/DATE | "")

POSITION == (LAT, LON, HEIGHT)

Only one track may be open for each user.. so if the user requests START and 
another track is open it gets closed immediately