确定Java Azure IoT中心DeviceClient连接状态？

Question

Is there a way to determine if the client is/isn't connected using the client SDK? I see how to do that using the JavaScript and .NET SDKS, but I don't see anything similar in the Java version of DeviceClient. What am I missing?

Answer 1

I'm not familiar with Java SDK, but as I know Java SDK does not support event trigger.

I'm afraid you have to check connection state before sending data as official SDK does https://github.com/Azure/azure-iot-sdk-java/blob/master/device/iot-device-client/src/main/java/com/microsoft/azure/sdk/iot/device/DeviceClient.java#L250

Also, Java SDK use loop to receive messages, but not MQTT subscription https://github.com/Azure/azure-iot-sdk-java/blob/master/device/iot-device-client/src/main/java/com/microsoft/azure/sdk/iot/device/DeviceClient.java#L197

So maybe you need to handle a schedule to check state as well.

Answer 2

In Java SDK, when you send event, it will be pushed to a waiting list. There is a thread to consume and send message in this list.

I tried to close the network connection when the device is sending messages per second. Since there's a lock on the waiting list, so the consuming thread will be stuck. The message will retain in the waiting list. After the connection is recovered, message in the waiting list will be sent.

There isn't a way to get the status of the waiting list. Maybe here's a work-around for you requirement, you can maintain a processing counter. When you send message, increment the counter, and meanwhile you register a callback which will decrement the counter. You can check the counter to proximately "guess" the connection state.