The Modbus Organization maintains a database of Modbus devices as a service to users looking for such devices for their applications. Serial Communications and via TCP/IP MODBUS RTU ASCII Modus. Modbus protocol library for TCP RTU over TCP. Perform easily Modbus master or slave device functionality in your application written for example with C++, C#, Delphi, Pascal, Visual Basic (incl. Modbus Library with Master, Client and Slave support. Modbus Library Data transmission library using MODBUS Protocol Driver.