is thread safe of connect()?

[xuzhaofangxzf]

as describe in [tutorials] int connect(std::string const & uri) { websocketpp::lib::error_code ec;

     client::connection_ptr con = m_endpoint.get_connection(uri, ec);

     if (ec) {
         std::cout << "> Connect initialization error: " << ec.message() << std::endl;
         return -1;
     }

     int new_id = m_next_id++;
     connection_metadata::ptr metadata_ptr = websocketpp::lib::make_shared<connection_metadata>(new_id, con->get_handle(), uri);
     m_connection_list[new_id] = metadata_ptr;

     con->set_open_handler(websocketpp::lib::bind(
         &connection_metadata::on_open,
         metadata_ptr,
         &m_endpoint,
         websocketpp::lib::placeholders::_1
     ));
     con->set_fail_handler(websocketpp::lib::bind(
         &connection_metadata::on_fail,
         metadata_ptr,
         &m_endpoint,
         websocketpp::lib::placeholders::_1
     ));
     con->set_close_handler(websocketpp::lib::bind(
         &connection_metadata::on_close,
         metadata_ptr,
         &m_endpoint,
         websocketpp::lib::placeholders::_1
     ));
     con->set_message_handler(websocketpp::lib::bind(
         &connection_metadata::on_message,
         metadata_ptr,
         websocketpp::lib::placeholders::_1,
         websocketpp::lib::placeholders::_2
     ));

     m_endpoint.connect(con);

     return new_id;
 }

is thread safe when call the connect function?