public class BufferedConnection
    {  
        ...

        private BlockingCollection<NetworkRequest> _queue;
        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
       
        ...

        // отправка запроса - ставит запрос в очередь и блокирует вызывающий поток до получения ответа либо тайм-аута:
        public byte[] Send(byte[] requestBytes)
        {
            var request = new NetworkRequest(requestBytes);
             _queue.Add(request);            
            var waitResult = request.ProcessedWaitEvent.Wait(TimeSpan.FromMilliseconds(ReceiveTimeoutMilliseconds));
            if (!waitResult)
            {
                // не дождались - говорим, что отправлять запрос не нужно
                request.ShouldBeProcessed = false;
            }
            return waitResult ? request.ResponseBytes : null;
        }               

        //  обработка очереди:
        private void ProcessorTaskMethod()
        {
            var token = _cancellationTokenSource.Token;
            while (!_cancellationTokenSource.IsCancellationRequested)
            {
                try
                {
                    var request = _queue.Take(token);
                    if (!request.ShouldBeProcessed) continue;   
                    request.ResponseBytes = SomeProcessingLogic(...);
                    request.ProcessedWaitEvent.Set();
                }
                catch (OperationCanceledException oce)
                {
                    break;
                }
            }
        }        
        
        ...

    }

var waitResult = request.ProcessedWaitEvent.Wait(TimeSpan.FromMilliseconds(ReceiveTimeoutMilliseconds));

request.ShouldBeProcessed = false;

 if (!request.ShouldBeProcessed) continue;  

public class NetworkRequest 
    {
        public byte[] RequestBytes { get; private set; }
        public byte[] ResponseBytes { get;  set; }
        public bool ShouldBeProcessed { get; set; }
        private ManualResetEventSlim _resetEvent = new ManualResetEventSlim(false);

        public ManualResetEventSlim ProcessedWaitEvent
        {
            get { return _resetEvent; }
        }

        public NetworkRequest(byte[] requestDataBytes)
        {
            RequestBytes = requestDataBytes;
            ShouldBeProcessed = true;
        }
       
    }

    [MethodImpl(MethodImplOptions.Synchronized)]
    public byte[] Send(byte[] requestBytes)
    {
        ...
    }