C# Handling threads and blocking sockets

Question

In the following thread, UDP packets are read from clients until the boolean field Run is set to false.

If Run is set to false while the Receive method is blocking, it stays blocked forever (unless a client sends data, which will make the thread loop and check for the Run condition again).

while (Run)
{
    IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
    byte[] data = udpClient.Receive(ref remoteEndPoint); // blocking method

    // process received data
}

I usually get around the problem by setting a timeout on the server. It works fine, but seems to be a patchy solution to me.

udpClient.Client.ReceiveTimeout = 5000;

while (Run)
{
    try
    {
        IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
        byte[] data = udpClient.Receive(ref remoteEndPoint); // blocking method

        // process received data
    }
    catch(SocketException ex) {} // timeout reached
}

How would you handle this problem? Is there any better way?

Hans Passant · Accepted Answer · 2011-04-02 20:49:10Z

3

Use UdpClient.Close(). That will terminate the blocking Receive() call. Be prepared to catch the ObjectDisposedException, it signals your thread that the socket is closed.

answered Apr 2, 2011 at 20:49

Hans Passant

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Comments

rgmills · Accepted Answer · 2011-04-02 20:49:56Z

0

You could do something like this:

private bool run;
public bool Run
{
    get
    {
        return run;
    }

    set
    {
        run = value;
        if(!run) 
        {
            udpClient.Close();
        }

    }   
}

This allows you to close the client once whatever condition is met to stop your connection from listening. An exception will likely be thrown, but I don't believe it will be a SocketTimeoutException, so you'll need to handle that.

answered Apr 2, 2011 at 20:49

rgmills

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1 Comment

zezba9000 Over a year ago

Just call disconnect before you call close and it won't throw an exception.

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