Provide getter for broadcast BIP socket (#350)

ports/win32/bip-init.c

@@ -89,12 +89,25 @@ static void debug_print_ipv4(const char *str,
  * @return The active BIP socket, or INVALID_SOCKET if uninitialized.
  * @note Strictly, the return type should be SOCKET, however in practice 
  *  Windows never returns values large enough that truncation is an issue.
+ * @see bip_get_broadcast_socket
  */
 int bip_get_socket(void)
 {
     return (int)BIP_Socket;
 }
 
+/**
+ * @brief Return the active BIP Broadcast socket.
+ * @return The active BIP Broadcast socket, or INVALID_SOCKET if uninitialized.
+ * @note Strictly, the return type should be SOCKET, however in practice
+ *  Windows never returns values large enough that truncation is an issue.
+ * @see bip_get_socket
+ */
+int bip_get_broadcast_socket(void)
+{
+    return (int)BIP_Broadcast_Socket;
+}
+
 /**
  * @brief Enabled debug printing of BACnet/IPv4
  */