Find through which network device user is connected to internet

Question

Using the code below I will get all network interfaces which are enabled and functional on the machine.

Private netIntrfc As NetworkInterface() = NetworkInterface.GetAllNetworkInterfaces()
For i As Integer = 0 To netIntrfc.Length - 1
  If netIntrfc(i).OperationalStatus = OperationalStatus.Up Then
    netDevicesList.Items.Add(netIntrfc(i).Name.ToString)
  End If
Next

But my problem is how to get the default one, the one(ethernet adapter) through which user is connected to internet?

I need to change some settings of default(through which user is connected to internet) adapter. settings I change through registry so I could sample add same settings for each network interface but that could cause problems and makes no point then.

EDITED:

For now I have done like code below, so if this can help someone other, but if someone has a better solution or more reliable then send please.

Dim u As UdpClient = New UdpClient(System.Net.Dns.GetHostName, 1)
Dim localAddr As IPAddress = CType(u.Client.LocalEndPoint, IPEndPoint).Address

Private netIntrfc As NetworkInterface() = NetworkInterface.GetAllNetworkInterfaces()
For i As Integer = 0 To netIntrfc.Length - 1
  If netIntrfc(i).OperationalStatus = OperationalStatus.Up Then
    For Each uni As NetworkInformation.UnicastIPAddressInformation In ipProps.UnicastAddresses
      If uni.Address.ToString = localAddr.ToString Then
        netDevicesList.Items.Add("DEFAULT: " & netIntrfc(i).Name.ToString)
        DEFDEVID = netIntrfc(i).Id.ToString
      End If
    Next
    netDevicesList.Items.Add(netIntrfc(i).Name.ToString)
  End If
Next

Thanks Thomas-Li and this post

Will this give you some hints? http://stackoverflow.com/questions/359596/identifying-active-network-interface-in-net — Thomas Li, Apr 01 '11 at 22:38
yep that helped me :) hope it will work ok i dont have much resources to test this out but as for me on my pc with 3 ethernet cards and one wireless it works ok :) thank you. you can post as answer so i accept you ;) — FeRtoll, Apr 01 '11 at 23:02

score 1 · Accepted Answer · edited May 23 '17 at 12:08

1

Will this give you some hints?

Identifying active network interface

edited May 23 '17 at 12:08

Community

1
1

answered Apr 01 '11 at 23:06

Thomas Li

3,358
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score -1 · Answer 2 · answered Apr 13 '13 at 15:04

i ported your code to c#, i hope you don' t mind

    static void Main(string[] args)
    {
        UdpClient u = new UdpClient(System.Net.Dns.GetHostName(), 1);
        IPAddress localAddr = (u.Client.LocalEndPoint as IPEndPoint).Address;
        NetworkInterface[] netIntrfc  = NetworkInterface.GetAllNetworkInterfaces();
        for (int i = 0; i < netIntrfc.Length - 1; i++)
        {
            if (netIntrfc[i].OperationalStatus == OperationalStatus.Up) 
            {
                IPInterfaceProperties ipProps = netIntrfc[i].GetIPProperties();
                foreach (UnicastIPAddressInformation uni in ipProps.UnicastAddresses) 
                {
                    if (uni.Address.ToString() == localAddr.ToString()) 
                    {
                        Console.WriteLine("DEFAULT: " + netIntrfc[i].Name.ToString());
                        Console.WriteLine(netIntrfc[i].Id.ToString());
                    }
                }
            } 
        }
    }

Find through which network device user is connected to internet

2 Answers2