I'm so sorry but the last bugfix release 1.1.3 has provided some regression for RTU viaTCP protocol (see issue #23). Thanks @pwood without him I wouldn't have known about it so quick. Now bug has been fixed and checked for RTU and RTU via TCP protocols. Also I have deleted a stupid delays in the reading requests and I have improved speed this part of library several times. Please update your gems and use the new version of RModBus.