Enable multicast groups

Author: sebromero

libraries/WiFi/src/WiFiUdp.cpp

@@ -39,6 +39,22 @@ uint8_t arduino::WiFiUDP::begin(uint16_t port) {
     return 1;
 }
 
+uint8_t arduino::WiFiUDP::beginMulticast(IPAddress ip, uint16_t port) {
+    // success = 1, fail = 0
+    if(begin(port) != 1){
+        return 0;
+    }
+
+    nsapi_addr_t multicastGroup = {NSAPI_IPv4, {ip[0], ip[1], ip[2], ip[3]}};       
+
+    if (_socket.join_multicast_group(SocketAddress(multicastGroup)) != NSAPI_ERROR_OK) {
+        printf("Error joining the multicast group\n");
+        return 0;
+    }
+
+    return 1;
+}
+
 void arduino::WiFiUDP::stop() {
     _socket.close();    
 }

libraries/WiFi/src/WiFiUdp.h

@@ -47,7 +47,7 @@ class WiFiUDP : public UDP {
   WiFiUDP();  // Constructor
   ~WiFiUDP();
   virtual uint8_t begin(uint16_t);	// initialize, start listening on specified port. Returns 1 if successful, 0 if there are no sockets available to use
-  // virtual uint8_t beginMulticast(IPAddress, uint16_t);  // initialize, start listening on specified multicast IP address and port. Returns 1 if successful, 0 if there are no sockets available to use
+  virtual uint8_t beginMulticast(IPAddress, uint16_t);  // initialize, start listening on specified multicast IP address and port. Returns 1 if successful, 0 if there are no sockets available to use
   virtual void stop();  // Finish with the UDP socket
 
   // Sending UDP packets