Fix calling WiFiUDP::begin(...) twice failing

Author: sandeepmistry

src/WiFiUdp.cpp

@@ -46,6 +46,11 @@ uint8_t WiFiUDP::begin(uint16_t port)
 	addr.sin_port = _htons(port);
 	addr.sin_addr.s_addr = 0;
 
+	if (_socket != -1 && WiFiSocket.bound(_socket)) {
+		WiFiSocket.close(_socket);
+		_socket = -1;
+	}
+
 	// Open UDP server socket.
 	if ((_socket = WiFiSocket.create(AF_INET, SOCK_DGRAM, 0)) < 0) {
 		return 0;

src/utility/WiFiSocket.cpp

@@ -172,6 +172,13 @@ uint8 WiFiSocketClass::listening(SOCKET sock)
 	return (_info[sock].state == SOCKET_STATE_LISTENING);
 }
 
+uint8 WiFiSocketClass::bound(SOCKET sock)
+{
+	m2m_wifi_handle_events(NULL);
+
+	return (_info[sock].state == SOCKET_STATE_BOUND);
+}
+
 int WiFiSocketClass::available(SOCKET sock)
 {
 	m2m_wifi_handle_events(NULL);

src/utility/WiFiSocket.h

@@ -40,6 +40,7 @@ class WiFiSocketClass {
   sint8 connect(SOCKET sock, struct sockaddr *pstrAddr, uint8 u8AddrLen);
   uint8 connected(SOCKET sock);
   uint8 listening(SOCKET sock);
+  uint8 bound(SOCKET sock);
   int available(SOCKET sock);
   int peek(SOCKET sock);
   int read(SOCKET sock, uint8_t* buf, size_t size);