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Protocol Matrix

This is the first page to open when you want to know what communication protocols and transport surfaces truST supports.

flowchart LR A[Need connectivity] --> B[truST runtime on the other side?] B -->|Yes| C[Runtime-to-runtime
discovery / mesh / realtime T0 / runtime-cloud] B -->|No| D[External software or plant system?] D -->|Yes| E[External systems
Modbus TCP / MQTT / OPC UA] D -->|No| F[Local hardware or fieldbus
EtherCAT / GPIO / simulated / loopback / multi-driver]

Figure: Start with the endpoint class. Runtime federation, external software integration, and direct hardware wiring are different problem families and branch to different docs sections.

By problem type

Question Start here Typical surfaces
How do I connect two truST runtimes? Runtime-to-runtime discovery, mesh/Zenoh, realtime T0, runtime-cloud federation
How do I connect truST to another system? External systems Modbus TCP, MQTT, OPC UA
How do I connect to local hardware or fieldbus? Devices and fieldbus EtherCAT, GPIO, simulated, loopback, multi-driver

Runtime-to-runtime

Surface Best for Go to
discovery finding peers and bootstrapping trust on a LAN Discovery And Pairing
mesh / Zenoh explicit runtime-to-runtime data sharing Mesh And Zenoh
realtime / T0 same-host deterministic transport Realtime T0
runtime-cloud / web federation, fleet, dispatch, browser control plane Runtime Cloud Federation

External systems

Protocol Best for Go to
Modbus TCP register-oriented PLC/device integration Modbus TCP
MQTT brokered event/message exchange MQTT
OPC UA runtime variable exposure to OPC UA clients OPC UA

Device and fieldbus drivers

Driver Best for Go to
EtherCAT deterministic fieldbus I/O EtherCAT
GPIO direct edge/local pin mapping GPIO
simulated fake process inputs without hardware Simulated And Loopback
loopback fast local %Q -> %I sanity checks Simulated And Loopback
multi-driver one runtime talking to more than one driver family Multi Driver

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