6 - Class C: Continuously Listening for Downlinks
End devices in Class C mode listen for downlinks except when they are broadcasting Class A uplinks, or the Class A receive windows are open.
Class C mode is enabled by identifying the end device as a Class C capable device when you register it on the network server. The network server will then immediately send any downlinks it receives over a single gateway.
How to Send Class C Messages
Class C downlinks are sent to a device from the network server. Each network server may support different options for sending downlinks, for example, the use of APIs to enable programmatic integration, or a user interface to enable manual submission of messages. The network server then broadcasts the downlink to the device over the gateway it determines has the best chance of reaching the device. When a device is registered with the network server as a Class C device, the network server will broadcast the message immediately.
Note
The network server selects the gateway it will use by identifying which has the highest chance of ensuring the message is received by the device, based on the gateways it recently received Class A uplinks from.
Because the network server uses statistics from recent Class A uplinks it has received to select the gateway, it is important that the end device sends regular Class A uplinks to the network server. This was discussed in the section Updating the Network Downlink Route.