public async ValueTask HandleMessage(IActivityMonitor m,
string topic, PipeReader pipe, int payloadLength, QualityOfService qos, bool retain, CancellationToken cancelToken)
{
Memory <byte> memory = new(new byte[payloadLength]);
FillStatus status = await pipe.CopyToBuffer(memory, cancelToken);
if (status != FillStatus.Done)
{
throw new InvalidOperationException("Unexpected partial read.");
}
await _messageHandler(m, new ApplicationMessage( topic, memory, qos, retain ), cancelToken);
}