title: Is RTU over TCP a spec-conforming modbus application?
body: <p>For a week I've played with cheap modbus RS485/Ethernet adapters like USR-TCP232-304. I was assuming they would "speak" modbus TCP on the ethernet side and modbus RTU over RS485. After countless experiments I've found what that these adapters are <em>actually</em> expecting is RTU over TCP on the ethernet side, so they're not repackaging the ADU/PDU but simply relay.</p>
  
  <p>Is this a standardized way of doing modbus or do I simply misunderstand what's going on?</p>