Add hasClient for BluetoothSerial (#1183)

* Add hasClient for BluetoothSerial

* Add SPP_TAG

libraries/BluetoothSerial/keywords.txt

@@ -19,7 +19,7 @@ BluetoothSerial	KEYWORD1
 #######################################
 
 SerialBT	KEYWORD2
-
+hasClient	KEYWORD2
 
 #######################################
 # Constants (LITERAL1)

libraries/BluetoothSerial/src/BluetoothSerial.cpp

@@ -29,6 +29,7 @@
 #include "esp_spp_api.h"
 
 #define SPP_SERVER_NAME "ESP32_SPP_SERVER"
+#define SPP_TAG "BluetoothSerial"
 
 #define QUEUE_SIZE 256
 uint32_t client;
@@ -188,6 +189,14 @@ int BluetoothSerial::peek(void)
     return -1;
 }
 
+bool BluetoothSerial::hasClient(void)
+{
+    if (client)
+        return true;
+	
+    return false;
+}
+
 int BluetoothSerial::read(void)
 {
     if (available()){

libraries/BluetoothSerial/src/BluetoothSerial.h

@@ -40,6 +40,7 @@ class BluetoothSerial: public Stream
         bool begin(String localName=String());
         int available(void);
         int peek(void);
+        bool hasClient(void);
         int read(void);
         size_t write(uint8_t c);
         size_t write(const uint8_t *buffer, size_t size);