Question

Is my use of ConcurrentQueue here between 2 threads ok? I wanted to check I don’t need to “lock” anywhere explicitly. In particular look at the lines where I have in COMMENTS would I drop a packet here…

public class PacketCapturer
{

private static ConcurrentQueue<Packet> _packetQueue = new ConcurrentQueue<Packet>();

public PacketCapturer(IPHostEntry proxyDns, ref BackgroundWorker bw)
{
    // start the background thread
    var backgroundThread = new System.Threading.Thread(BackgroundThread);
    backgroundThread.Start();

    // Start Packet Capture with callback via PacketCapturerCallback
}

private void PacketCapturerCallback(Packet packet)
{
    _packetQueue.Enqueue(packet);
}

private static void BackgroundThread()
{
    while (!BackgroundThreadStop)
    {
        if (_packetQueue.Count == 0) Thread.Sleep(250);
        else 
        {
            ConcurrentQueue<Packet> ourQueue;  
            ourQueue = _packetQueue;   // COULD I DROP A PACKET BETWEEN HERE
            _packetQueue = new ConcurrentQueue<Packet>();      // AND HERE???

            Console.WriteLine("BackgroundThread: ourQueue.Count is {0}", ourQueue.Count);
        }
    }
}

Answer 1

Edit: I think Mark/Gabe are right that you won’t lose any Packets. I’ll leave the rest in just for reference in case anyone else can weigh in on this.

---

Simply, yes. You could lose one or more Packets there. You might want to look into what methods ConcurrentQueue offers to get/remove a portion of it as that looks like what you want to do.

Why not TryDequeue until it returns false:

    else 
    {
        Queue<Packet> ourQueue = new Queue<Packet>();  //this doesn't need to be concurrent unless you want it to be for some other reason.
        Packet p;
        while(_packetQueue.TryDequeue(out p))
        {
            ourQueue.Enqueue(p);
        }

        Console.WriteLine("BackgroundThread: ourQueue.Count is {0}", ourQueue.Count);
    }