public async Task <bool> SendMqttMessageAsync(string topic, byte[] data, CancellationToken cancellationToken)
{
if (data.Length > 1548)
{
throw new Exception("Message is too long!");
}
if (_module.CurrentBinaryWriteTask != null)
{
throw new Exception("Cannot create another binary write task when one is already queued!");
}
var command = $"AT+QMTPUB={CurrentTcpConnectId},{_currentMessageId},{DefaultQOS},{(ShouldServerRetain ? 1 : 0)},\"{topic}\"";
_currentMessageId++;
_module.WriteLine(command);
var waitTaskSource = new TaskCompletionSource <bool>();
_module.CurrentBinaryWriteTask = waitTaskSource;
var waitTaskResult = await waitTaskSource.Task;
_module.CurrentBinaryWriteTask = null; //very important!
if (waitTaskResult)
{
_module.BaseSerialPort.Write(data, 0, data.Length);
_module.BaseSerialPort.Write("\u001A");
}
else
{
throw new Exception("Waiting for binary read signal failed!");
}
var waitResponseSource = new TaskCompletionSource <CommandResult>();
_module.AtCommandResultQueue.AddFirst(waitResponseSource); //push to top of queue, since we should be there anyways and we had received the > char
var result = await waitResponseSource.Task;
result.ThrowIfError();
return(!result.WasCMEError && result.Result == ATCommandResultCode.OK);
}
