go-modbus
Modbus client and server for the functions of the specification: TCP, RTU, ASCII, TLS and UDP, typed register codecs, pooling, retries and a PDU tap for recording.
go get github.com/otfabric/go-modbusUI apps
Modbus Trace Explorer
Open a packet trace of Modbus/TCP traffic and see it in Modbus terms: every request with its response, per device, per poll and per register. Then export the real traffic to replay as a simulated device.
What it does
- Latency per device and per unit behind a gateway, with quantiles and a histogram: which device holds up the cycle.
- Poll plans per client: what each client reads, how often, how regularly and how often the answer changes. Duplicate polling and cycles that overrun their interval show at once.
- Exceptions, unanswered requests and gateway errors explained in words, with a filter grammar such as status:exception unit:4 addr:holding/4096-4160.
- What was read and written per device, and the values of one register over time with the writes marked. Every connection with its role, resets, gaps and retransmissions.
- Export one device, the current filter or everything as an MBCAP capture, with a preview of what goes in and why the rest stays out, ready for modbusctl server replay. Also CSV, JSON Lines and a pcapng sub-trace.
- Reads pcap and pcapng from tcpdump, Wireshark, dumpcap or tshark, ring buffers and gzip files as they are, and MBCAP captures. A million rows page, filter and sort in milliseconds.
- Read-only and offline: it never talks to devices, never writes to Modbus and does not capture live. A desktop application for macOS, Windows and Linux.
See it in action
Protocols
- Modbus: The most widely deployed protocol in industrial automation: meters, inverters, batteries, drives and PLCs.
The README on GitHub has the full feature list, examples and changelog.
Related projects
go-modbus-capture
MBCAP, the capture format for what Modbus devices answered and when, so a virtual device can serve it again. Go library and mbcapctl to inspect, verify, convert, filter, merge and repair captures.
go get github.com/otfabric/go-modbus-capturego-modbus-trace
Read pcap and pcapng traces of Modbus/TCP offline: transactions, devices, poll patterns and address coverage. Library and mbtracectl, with timeline, sub-trace and MBCAP export.
go get github.com/otfabric/go-modbus-trace
go-sunspec
SunSpec over Modbus, both sides: discovers and decodes 112 built-in models into typed, scaled values, and serves simulated or real SunSpec devices.
go get github.com/otfabric/go-sunspecmodbus-simulator
Deterministic, stateful Modbus TCP and TLS device simulator driven by JSON fixtures, with fault injection, request traces and CI assertions.
modbusctl
Identify, fingerprint, scan, poll, decode and write Modbus devices over TCP, serial and TLS. Record them to MBCAP capture files and replay those as a simulated device.
sunspecctl
Detect, list, read and poll SunSpec inverters, meters and batteries, and serve a simulated device from a JSON file or a capture of a real one.
go-serial
Cross-platform serial ports for RS-232 and RS-485, with a Modbus RTU preset.
go get github.com/otfabric/go-serialmodbus-interop
Modbus TCP reference stacks: libmodbus, PyModbus, digitalpetri, NModbus and tokio-modbus.
SunSpec Explorer
Connect to a SunSpec inverter, meter or battery and see every model it exposes fully decoded. Read once or poll, record and export, without ever writing to the device.