Implemented UDP hole punch.

src/utility/config_utility.hpp

@@ -41,7 +41,7 @@ inline auto LOAD_FLOAT_ITEM2(const nlohmann::json &config,
 inline auto LOAD_UINT_ITEM2(const nlohmann::json &config,
                             const std::string &item_name) {
     assert(config.contains(item_name));
-    assert(config[item_name].is_boolean());
+    assert(config[item_name].is_number_integer());
     return config[item_name].get<uint64_t>();
 }