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[Bug Report] ClassCastException: class com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection cannot be cast to class com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection #1853
OS and version used: amazoncorretto:25-alpine-jdk (Dockerfile)
Java runtime used: 25.0.2
SDK version used: 2.5.1
Description of the issue
We have some DeviceClients - using the IotHubClientProtocol.MQTT - that connects, sends and close their connection afterwards.
In case the IoTHub is not available at the moment that DeviceClients try to reconnect to it causing the following exception:
java.lang.ClassCastException: class com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection cannot be cast to class com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection (com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection and com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection are in unnamed module of loader org.springframework.boot.loader.launch.LaunchedClassLoader @3c27f72)
at com.microsoft.azure.sdk.iot.device.transport.IotHubTransport.singleDeviceReconnectAttemptAsync(IotHubTransport.java:1464)
at com.microsoft.azure.sdk.iot.device.transport.IotHubTransport.reconnect(IotHubTransport.java:649)
at com.microsoft.azure.sdk.iot.device.transport.IotHubReconnectTask.run(IotHubReconnectTask.java:94)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:545)
at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:369)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:310)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:614)
at java.base/java.lang.Thread.run(Thread.java:1474)
Since the IoTHub is seldom out of order we do not see that exception very often. But when it is there are a lot of devices that try to reconnect causing a lot of exceptions for a very short time range.
changed the title [-][Bug Report][/-][+][Bug Report] ClassCastException: class com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection cannot be cast to class com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection[/+]on Jul 30, 2026
Activity
[-][Bug Report][/-][+][Bug Report] ClassCastException: class com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection cannot be cast to class com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection[/+]