UDP port open check

Question

What is the best way to check if the UDP port is open or not on the same machine. I have got port number 7525UDP and if it\'s open I would like to bind to it. I

Answer 1

int myport = 7525;
bool alreadyinuse = System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().GetActiveUdpListeners().Any(p => p.Port == myport);

A comment below suggested a variation which would supply the first free UDP port... however, the suggested code is inefficient as it calls out to the external assembly multiple times (depending on how many ports are in use). Here's a more efficient variation which will only call the external assembly once (and is also more readable):

    var startingAtPort = 5000;
    var maxNumberOfPortsToCheck = 500;
    var range = Enumerable.Range(startingAtPort, maxNumberOfPortsToCheck);
    var portsInUse = 
        from p in range
            join used in System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().GetActiveUdpListeners()
                on p equals used.Port
                    select p;

    var FirstFreeUDPPortInRange = range.Except(portsInUse).FirstOrDefault();

    if(FirstFreeUDPPortInRange > 0)
    {
         // do stuff
         Console.WriteLine(FirstFreeUDPPortInRange);
    } else {
         // complain about lack of free ports?
    }