Add BTSerialInterface isClosed

Author: PaulZC

Firmware/RTK_Everywhere/bluetoothSelect.h

@@ -33,6 +33,7 @@ class BTSerialInterface : public virtual Stream
                          esp_spp_sec_t sec_mask = (ESP_SPP_SEC_ENCRYPT | ESP_SPP_SEC_AUTHENTICATE),
                          esp_spp_role_t role = ESP_SPP_ROLE_MASTER) = 0; // Needed for Apple Accessory
     virtual bool connected() = 0;
+    virtual bool isClosed() = 0;
     virtual void enableSSP(bool inputCapability, bool outputCapability) = 0;
     virtual bool aclConnected() = 0;
     virtual uint8_t *aclGetAddress() = 0;
@@ -117,6 +118,11 @@ class BTClassicSerial : public virtual BTSerialInterface, public BluetoothSerial
         return (BluetoothSerial::connected());
     }
 
+    bool isClosed()
+    {
+        return (BluetoothSerial::isClosed());
+    }
+
     void enableSSP(bool inputCapability, bool outputCapability)
     {
         return (BluetoothSerial::enableSSP(inputCapability, outputCapability));
@@ -216,6 +222,11 @@ class BTLESerial : public virtual BTSerialInterface, public BleSerial
         return (BleSerial::connected());
     }
 
+    bool isClosed()
+    {
+        return false;
+    }
+
     void enableSSP(bool inputCapability, bool outputCapability) {}
 
     bool aclConnected()