- Used by the `modbus' plugin to communicate with Modbus/TCP devices.
- <https://launchpad.net/libmodbus>
+ Used by the “modbus” plugin to communicate with Modbus/TCP devices. The
+ “modbus” plugin works with version 2.0.3 of the library – due to frequent
+ API changes other versions may or may not compile cleanly.
+ <http://www.libmodbus.org/>