How do I determine the local host’s IPv4 addresses?

Question

How do I get only Internet Protocol version 4 addresses from Dns.GetHostAddresses()? I have the code below, and it gives me IPv4 and IPv6 addresses. I have to make it work with boxes that have multiple IPv4 addresses.

IPAddress[] localIPs = Dns.GetHostAddresses(Dns.GetHostName()); private void get_IPs()     {         foreach (IPAddress a in localIPs)         {            server_ip = server_ip + a.ToString() + "/";         }     } 

Answer 1

From my blog:

/// <summary>  /// This utility function displays all the IP (v4, not v6) addresses of the local computer.  /// </summary>  public static void DisplayIPAddresses()  {      StringBuilder sb = new StringBuilder();       // Get a list of all network interfaces (usually one per network card, dialup, and VPN connection)      NetworkInterface[] networkInterfaces = NetworkInterface.GetAllNetworkInterfaces();       foreach (NetworkInterface network in networkInterfaces)      {          // Read the IP configuration for each network          IPInterfaceProperties properties = network.GetIPProperties();           // Each network interface may have multiple IP addresses          foreach (IPAddressInformation address in properties.UnicastAddresses)          {              // We're only interested in IPv4 addresses for now              if (address.Address.AddressFamily != AddressFamily.InterNetwork)                  continue;               // Ignore loopback addresses (e.g., 127.0.0.1)              if (IPAddress.IsLoopback(address.Address))                  continue;               sb.AppendLine(address.Address.ToString() + " (" + network.Name + ")");          }      }       MessageBox.Show(sb.ToString());  } 

In particular, I do not recommend Dns.GetHostAddresses(Dns.GetHostName());, regardless of how popular that line is on various articles and blogs.

Answer 2

add something like this to your code

  if( IPAddress.Parse(a).AddressFamily == AddressFamily.InterNetwork )   // IPv4 address