Device Connectivity
Anytime a devices connects to a Golioth IoT Gateway (CoAP), the Gateway will track and report the status of the connection.
Rather than tracking just online / offline information, we keep a set of three timestamps for each device which can be used to dynamically compute the online or offline status:
| Timestamp | Update event |
|---|---|
| Last Report | Device interacts with a given service (LightDB State/Stream, Device Logs and other services). |
| Last Time Online | Device performs a successful handshake and authentication with a Golioth IoT Gateway |
| Last Time Offline | Depends on which protocol the device uses, see below. |
Online and Offline meaning on each protocol
The online / offline indication varies by protocol.
CoAP is based on UDP, a connectionless and stateless protocol which doesn't have a concept of online or offline. But since we are mandating the use of DTLS for all CoAP connections, we use the DTLS handshake and authentication as indication of a device going online. Since CoAP is frequently used in low power scenarios with infrequent communication, we don't send keepalives to devices. We keep every DTLS session stored for 3 hours, during which a device can resume it. If the device doesn't send any information for 3 hours or if it actively disconnects, we consider the device offline.
| Related configuration | Default Value |
|---|---|
| Session Timeout | Default is 3 hours. Can't be negotiated with the device. |
- More on authentication over each protocol: