How are the disconnection events triggered for LoRaWAN gateways?

Hi. The Basic Station LNS protocol uses WebSocket as the transport protocol: https://lora-developers.semtech.com/build/software/lora-basics/lora-basics-for-gateways/?url=tcproto.html.

WebSocket is a connection-oriented protocol. For graceful closing of the connection, there is a closing handshake: https://datatracker.ietf.org/doc/html/rfc6455#section-1-4. You can see this implemented in Basic Station here: https://github.com/lorabasics/basicstation/blob/ba4f85d80a438a5c2b659e568cd2d0f0de08e5a7/src/net.c#L639. If Basic Station shuts down, it will send this handshake, causing AWS IoT Core for LoRaWAN to detect the disconnection immediately.

For less graceful situations, such as sudden power loss, WebSocket has the ping-pong mechanism: https://datatracker.ietf.org/doc/html/rfc6455#section-5-5-2. Here is where Basic Station will send a pong if it receives a ping from the LNS: https://github.com/lorabasics/basicstation/blob/ba4f85d80a438a5c2b659e568cd2d0f0de08e5a7/src/net.c#L577-L592.

It takes ~2 minutes to detect disconnection if I cut power to my gateway.