Smart grid is an electrical grid that uses digital communication technology to monitor the status of power consumption and power quality in real time. By using this information, engineers can adjust the power generation and the load of power transmission and distribution to reduce power consumption and enhance the power grid’s reliability. In order to reap the benefits of smart grids, legacy systems need to be upgraded with minimal cost and efforts. Engineers have to seamlessly integrate legacy systems into new communication networks through protocol gateways that convert between Modbus RTU/ASCII/TCP, IEC 60870-5-101 and IEC 60870-5-104.