Check if a port is open

Question

I can\'t seem to find anything that tells me if a port in my router is open or not. Is this even possible?

The code I have right now doesn\'t really seem to work...<

Answer 1

For me, I needed something blocking until the connection to the port is available or after a certain amount of retries. So, I figured out this code:

public bool IsPortOpen(string host, int port, int timeout, int retry)
{
    var retryCount = 0;
    while (retryCount < retry)
    {
        if (retryCount > 0)
            Thread.Sleep(timeout);

        try
        {
            using (var client = new TcpClient())
            {
                var result = client.BeginConnect(host, port, null, null);
                var success = result.AsyncWaitHandle.WaitOne(timeout);
                if (success)
                    return true;

                client.EndConnect(result);
            }
        }
        catch
        {
            // ignored
        }
        finally { retryCount++; }
    }

    return false;
}

Hope this helps!