main loop :
listens to the udp channel
deciphers the udp message
checks if the sender is a new bus or not
send the message to database through a fifo
turns the ivy message into a pushlet event
send the event to web users
checks if there are some buses that doesn't send messages anymore
removes drone which belonged to dead buses
listens fifo queue and stores ivy messages in database
if the message has the DECONNECT type it also fills the end field corresponding
to this ivy session into the 'connexion' table