Dereference of a possibly null reference.

Make 'HandleClientAsync' a static method. (https://rules.sonarsource.com/csharp/RSPEC-2325)

Make sure that using this pseudorandom number generator is safe here. (https://rules.sonarsource.com/csharp/RSPEC-2245)

Fix this implementation of 'IDisposable' to conform to the dispose pattern. (https://rules.sonarsource.com/csharp/RSPEC-3881)

Make '_cancellationTokenSource' 'readonly'. (https://rules.sonarsource.com/csharp/RSPEC-2933)

This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

Cannot convert null literal to non-nullable reference type.

Non-nullable field '_listener' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Nullability of reference types in type of parameter 'state' of 'void UdpTimedSender.SendMessageCallback(object state)' doesn't match the target delegate 'TimerCallback' (possibly because of nullability attributes).