Practical Modbus TCP and RTU over TCP guides from the developer of Modbus TCP FieldKit.https://modbusapp.com/enhttps://modbusapp.com/blog/modbus-exception-codes/https://modbusapp.com/blog/modbus-exception-codes/What each Modbus exception code means, how to spot one in a frame, the usual cause of 01, 02, 03, 04, 0A and 0B, and how a real server deviates from the spec.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-float-word-order/https://modbusapp.com/blog/modbus-float-word-order/Why two Modbus registers decode to nonsense, what the word order names mean, and how to find the right order on a device, with real values captured from a server.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-function-codes/https://modbusapp.com/blog/modbus-function-codes/The Modbus function codes you need most: 01 to 06, 15 and 16, with quantity limits, real request and response frames, and the less common codes.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-register-addressing-40001/https://modbusapp.com/blog/modbus-register-addressing-40001/Why register 40001 is address 0 on the wire, how to tell 0-based from 1-based documentation, and a quick test that settles it on a real device.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-rtu-over-tcp-vs-modbus-tcp/https://modbusapp.com/blog/modbus-rtu-over-tcp-vs-modbus-tcp/The frame differences between Modbus TCP and RTU over TCP, transparent and gateway converter modes, how to tell which one you have, and the traps of each.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-tcp-frame-mbap/https://modbusapp.com/blog/modbus-tcp-frame-mbap/A real Modbus TCP request and response dissected field by field: Transaction ID, Protocol ID, Length, Unit ID, function code and data, plus the size limits.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-tcp-timeout-troubleshooting/https://modbusapp.com/blog/modbus-tcp-timeout-troubleshooting/Work through a Modbus TCP failure layer by layer: refused, timed out, connected but silent, gateway errors. Each symptom tells you what to check next.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-testing-tools-compared/https://modbusapp.com/blog/modbus-testing-tools-compared/Which Modbus tool fits which job: Modbus Poll, mbpoll, QModMaster, pymodbus and iPhone apps, including FieldKit. Platforms, protocols, prices and their limits.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/modbus-unit-id/https://modbusapp.com/blog/modbus-unit-id/What the Modbus TCP Unit ID does, what the implementation guide recommends for direct devices and gateways, and how to find the right one when a device stays silent.Fri, 30 Oct 2026 00:00:00 GMThttps://modbusapp.com/blog/test-modbus-tcp-without-plc/https://modbusapp.com/blog/test-modbus-tcp-without-plc/Test a Modbus TCP client or SCADA screen without hardware: a Python simulator with a working script, the FieldKit server on an iPhone, and when to use each one.Fri, 30 Oct 2026 00:00:00 GMT