If reading of hardware serial# (MAC) fails then readSerial function generates a runtime MAC adderss using devicePath value. This solves cases where UDPServer and Cemulator doesn't work with blank serials (and linkToProfile and 360SteeringWheel calibration linking to a certain gamepad).

DS4Windows/HidLibrary/HidDevice.cs

@@ -488,10 +488,6 @@ namespace DS4Windows
                 if (readFeatureData(buffer))
                     serial = String.Format("{0:X02}:{1:X02}:{2:X02}:{3:X02}:{4:X02}:{5:X02}",
                         buffer[6], buffer[5], buffer[4], buffer[3], buffer[2], buffer[1]);
-                else
-                    serial = BLANK_SERIAL;
-
-                return serial;
             }
             else
             {
@@ -507,11 +503,55 @@ namespace DS4Windows
                     MACAddr = $"{MACAddr[0]}{MACAddr[1]}:{MACAddr[2]}{MACAddr[3]}:{MACAddr[4]}{MACAddr[5]}:{MACAddr[6]}{MACAddr[7]}:{MACAddr[8]}{MACAddr[9]}:{MACAddr[10]}{MACAddr[11]}";
                     serial = MACAddr;
                 }
+            }
+
+            // If serial# reading failed then generate a dummy MAC address based on HID device path (WinOS generated runtime unique value based on connected usb port and hub or BT channel).
+            // The device path remains the same as long the gamepad is always connected to the same usb/BT port, but may be different in other usb ports. Therefore this value is unique
+            // as long the same device is always connected to the same usb port.
+            if (serial == null)
+            {
+                string MACAddr = string.Empty;
+
+                AppLogger.LogToGui($"WARNING: Failed to read serial# from a gamepad ({this._deviceAttributes.VendorHexId}/{this._deviceAttributes.ProductHexId}). Generating MAC address from a device path. From now on you should connect this gamepad always into the same USB port or BT pairing host to keep the same device path.", true);
+
+                try
+                {
+                    // Substring: \\?\hid#vid_054c&pid_09cc&mi_03#7&1f882A25&0&0001#{4d1e55b2-f16f-11cf-88cb-001111000030} -> \\?\hid#vid_054c&pid_09cc&mi_03#7&1f882A25&0&0001#
+                    int endPos = this.DevicePath.LastIndexOf('{');
+                    if (endPos < 0)
+                        endPos = this.DevicePath.Length;
+
+                    // String array: \\?\hid#vid_054c&pid_09cc&mi_03#7&1f882A25&0&0001# -> [0]=\\?\hidvid_054c, [1]=pid_09cc, [2]=mi_037, [3]=1f882A25, [4]=0, [5]=0001
+                    string[] devPathItems = this.DevicePath.Substring(0, endPos).Replace("#", "").Replace("-", "").Replace("{", "").Replace("}", "").Split('&');
+
+                    if (devPathItems.Length >= 3)
+                        MACAddr = devPathItems[devPathItems.Length - 3].ToUpper()                   // 1f882A25
+                                  + devPathItems[devPathItems.Length - 2].ToUpper()                 // 0
+                                  + devPathItems[devPathItems.Length - 1].TrimStart('0').ToUpper(); // 0001 -> 1
+                    else if (devPathItems.Length >= 1)
+                        // Device and usb hub and port identifiers missing in devicePath string. Fallback to use vendor and product ID values and 
+                        // take a number from the last part of the devicePath. Hopefully the last part is a usb port number as it usually should be.
+                        MACAddr = this._deviceAttributes.VendorId.ToString("X4")
+                                  + this._deviceAttributes.ProductId.ToString("X4")
+                                  + devPathItems[devPathItems.Length - 1].TrimStart('0').ToUpper();
+
+                    if (!string.IsNullOrEmpty(MACAddr))
+                    {
+                        MACAddr = MACAddr.PadRight(12, '0');
+                        serial = $"{MACAddr[0]}{MACAddr[1]}:{MACAddr[2]}{MACAddr[3]}:{MACAddr[4]}{MACAddr[5]}:{MACAddr[6]}{MACAddr[7]}:{MACAddr[8]}{MACAddr[9]}:{MACAddr[10]}{MACAddr[11]}";
+                    }
                     else
+                        // Hmm... Shold never come here. Strange format in devicePath because all identifier items of devicePath string are missing.
                         serial = BLANK_SERIAL;
+                }
+                catch (Exception e)
+                {
+                    AppLogger.LogToGui($"ERROR: Failed to generate runtime MAC address from device path {this.DevicePath}. {e.Message}", true);
+                    serial = BLANK_SERIAL;
+                }
+            }
 
             return serial;
         }
     }
-    }
 }