Device Communication

            April 14, 2014

            LearnPadConnect relies on various communication methods to send commands to LearnPad devices, but the important distinction is between just two classes of control:

            Remote Control

            A remote control command will always be executed, even if it must wait until the device next connects to Wi-Fi. For instance, the device may actually be switched off when the command is issued, but it will be received once it is switched back on, anywhere there is an Internet connection, and whether it is in the school or not.

            This class of commands includes version upgrades and lesson profile changes: basically anything you wish to guarantee will happen, even if it takes a while.

             

            In-Class Control

            An in-class control command will only be received by devices active on the school’s Wi-Fi network at the time the command is issued. The command will not be stored for later or forwarded outside of the school network.

            This class of commands includes device pausing and audio alerts: commands that are either no use remotely or would cause unnecessary confusion to device users outside of the school.

             

            Communication Infrastructure

            The two classes of communication described above are supported by multiple overlapping systems to maximise reliability. Note that even though remote control commands are guaranteed to execute eventually, they will still use the fastest communication channel that is available.

            Server Commands

            The LearnPadConnect server stores remote control commands ready for the next time the device checks-in. For instance, devices can have a “pending lesson”, which is the lesson profile that should be assigned next.

            This is a pull system that relies on the device being able to contact the LearnPadConnect server at http://data.learnpad.co/. Remote control messages sent exclusively this way would only be processed when the device next calls in, which is typically on an hourly cycle.

            Google Cloud Messaging (GCM)

            Each device is registered with GCM, which provides a near real-time communication channel to devices anywhere in the world.

            GCM is a push system, which means commands can be processed very quickly, but it relies on the GCM ports (5228, 5229, and 5230) being open, which is not always the case on a school intranet. There is a test for diagnosing this on the device information page.

            LAN Connection

            LearnPadConnect can connect directly to each device if the Dashboard computer is on the same intranet as the LearnPads. For instance, if you are using your classroom PC to view the Dashboard, and it has an IP address of 192.168.0.66 and the LearnPad you want to communicate with is on the same intranet with an IP address of 192.168.0.69, then local LAN commands will work.

            To determine if this is possible, the Dashboard “pings” each LearnPad on the last known local IP address it had. This process is reported using device icons.

            In addition to communication between the LearnPad Dashboard and LearnPads, LearnPad devices may communicate directly with each other in order to exchange files and lesson data. This relies upon UDP broadcasts and as such, UDP broadcasts must be enabled on your wireless access points for this functionality to work. In the event that this functionality is not enabled on your wireless access points, LearnPad will download lesson content from the LearnPad servers instead.

            Firewall Configuration

            Your network firewall may need to be configured to allow all modes of LearnPad communication, see the firewall configuration guide for details.

            Our Wi-Fi troubleshooting guide helps you diagnose and fix network problems.


            Updated: 09 Apr 2018 02:03 AM
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