dpsenner
commented
6 years ago This is the minimal example showing the above exception messages:
public async Task RunAsync(CancellationToken cancellationToken)
{
var mqttFactory = new MqttFactory();
using (var mqttClient = mqttFactory.CreateMqttClient())
{
while (!cancellationToken.IsCancellationRequested)
{
// attempt to connect if not connected
if (await ConnectAsync(mqttClient))
{
// connection succeeded, do nothing for now
while (!cancellationToken.IsCancellationRequested && mqttClient.IsConnected)
{
await DelayAsync(TimeSpan.FromSeconds(1), cancellationToken);
}
}
}
// disconnect when cancellation is requested
await mqttClient.DisconnectAsync();
}
}
private async Task<bool> ConnectAsync(IMqttClient mqttClient)
{
try
{
var mqttClientOptions = BuildMqttClientOptions();
var connectResult = await mqttClient.ConnectAsync(mqttClientOptions);
return true;
}
catch (Exception ex)
{
// ignore this exception
Console.WriteLine($"Could not connect to {Server}:{Port}: {ex}");
return false;
}
}
private IMqttClientOptions BuildMqttClientOptions()
{
return new MqttClientOptions()
{
ClientId = ClientId,
ProtocolVersion = MQTTnet.Serializer.MqttProtocolVersion.V311,
CleanSession = false,
WillMessage = new MqttApplicationMessageBuilder()
.WithTopic("NDEATH")
.WithQualityOfServiceLevel(MqttQualityOfServiceLevel.ExactlyOnce)
.WithRetainFlag(true)
.Build(),
KeepAlivePeriod = TimeSpan.FromSeconds(15),
CommunicationTimeout = TimeSpan.FromSeconds(5),
KeepAliveSendInterval = TimeSpan.FromSeconds(5),
ChannelOptions = new MqttClientTcpOptions()
{
Server = Server,
Port = Port,
BufferSize = 4096,
TlsOptions = new MqttClientTlsOptions()
{
AllowUntrustedCertificates = true,
IgnoreCertificateChainErrors = true,
IgnoreCertificateRevocationErrors = true,
UseTls = false,
}
},
};
}
chkr1011
AtosNicoS
Expected behavior
When the mqtt broker is offline and ConnectAsync is invoked, an exception should be thrown that makes it clear that it cannot connect to the mqtt broker because it is unreachable.
Actual behavior
Interestingly, we observe a wide variety of exceptions and most of them are unrelated to the actual problem. Here's a list of the exceptions that we observed so far, the first being the most sensible of the following list: