Resolute User Manual Version 2.5
17
Iridium Tunnel and SBD Network Diagram
Upon reaching its start time, the tunnel will power on the configured modem and will attempt to
open a two way connection to XeosOnline (XO). The tunnel confirms two way operation to XO
via a heartbeat message known as a “keep alive”. A keep alive is a small data packet sent from
the unit to the XO server every 15 seconds and acknowledged by the server. This “keep alive”
message manages the connection between the unit and XO irrespective of any sockets being
opened by the user or a script. If two packets are unacknowledged in a row, the unit closes the
connection and tries to reestablish it.
Keep alive data packets include SOH information about the receiver, including voltage and
temperature conditions. Keep alive data packets are also the best way to verify the tunnel is
connected when your unit is in a remote location. If keep alives are coming in to the Message Log
of the unit every 15 seconds, the tunnel is connected.