Use DualMode

Author: nvborisenko

dotnet/src/webdriver/Internal/PortUtilities.cs

@@ -33,21 +33,10 @@ public static class PortUtilities
     /// <returns>A random, free port to be listened on.</returns>
     public static int FindFreePort()
     {
-        // Locate a free port on the local machine by binding a socket to
-        // an IPEndPoint using IPAddress.Any and port 0. The socket will
-        // select a free port.
-        try
-        {
-            using var socket = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
-            socket.Bind(new IPEndPoint(IPAddress.IPv6Loopback, 0));
-            return (socket.LocalEndPoint as IPEndPoint)!.Port;
-        }
-        catch (SocketException)
-        {
-            // If IPv6 is not supported, fallback to IPv4
-            using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
-            socket.Bind(new IPEndPoint(IPAddress.Loopback, 0));
-            return (socket.LocalEndPoint as IPEndPoint)!.Port;
-        }
+        using var socket = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
+        socket.DualMode = true;
+        socket.Bind(new IPEndPoint(IPAddress.IPv6Loopback, 0));
+        return (socket.LocalEndPoint as IPEndPoint)!.Port;
+
     }
 }