TRDP.NET

A pure C# / .NET port of the TCNOpen TRDP "Light" stack — the Train Real-time Data Protocol (TRDP), IEC 61375-2-3.

Process Data (PD) and Message Data (MD) over UDP/TCP, no native dependencies, runs anywhere .NET runs (x64 / ARM, Windows / Linux — including industrial PCs and the Kunbus Revolution Pi).

Status: 🚧 alpha. The complete TRDP "Light" stack and the full TAU application layer are ported and unit-tested (125 tests): FCS, PD/MD headers, VOS UDP+TCP, PD publish/subscribe, MD over UDP+TCP, marshalling (scalars/fixed+variable arrays/nested/strings), XML config, unified session, statistics, the TAU services (TTI, DNR, ECSP control, service interface), XML/comId marshalling, session-from-XML, and the indexed PD send timer. Validated live against the TCNOpen C reference. Everything except the SDTv2 safety layer is ported — see PORTING.md.

---

Why

TRDP is the standard real-time data protocol for modern train networks (TCN / ECN / ETB). The reference implementation TCNOpen TRDP is excellent but written in C for embedded targets. TRDP.NET brings it to managed .NET — no P/Invoke, no native build per platform, directly consumable from C# applications and frameworks.

Quickstart (Process Data)

using System.Net;
using Trdp.Net.Pd;

// One session per network interface; drive it from your main/control loop.
using var session = new TrdpPdSession(bindAddress: IPAddress.Any);

// Publish comId 1000 every 100 ms to a destination (unicast or multicast).
var pub = session.Publish(comId: 1000, destIp: IPAddress.Parse("239.1.1.1"), cycleTimeMs: 100);
pub.SetData(new byte[] { 0x01, 0x02, 0x03, 0x04 });

// Subscribe to comId 2000 with a 1 s timeout supervision.
var sub = session.Subscribe(comId: 2000, timeoutMs: 1000);
sub.DataReceived += s => Console.WriteLine($"got {s.LastData!.Length} bytes, seq {s.SequenceCounter}");
sub.Timeout += _ => Console.WriteLine("comId 2000 timed out");

while (running)
{
    session.Process();      // sends due telegrams, receives & dispatches, checks timeouts
    Thread.Sleep(5);
}

The loop-driven Process() model (no internal threads) maps cleanly onto a PLC-style cyclic executor.

Scope

Area	Status
FCS / CRC-32 (vos_crc32)	✅ ported + tested
PD / MD headers (wire format)	✅ ported + tested
Error model (TRDP_ERR_T)	✅ ported
VOS socket layer (UDP, BCL shim)	✅ ported
Process Data (PD) publish/subscribe	✅ core (cyclic send, receive, seq check, timeout)
Message Data (MD) over UDP	✅ notify / request-reply / confirm / listener
Message Data (MD) over TCP	✅ non-blocking listener/connect + stream reassembly
Marshalling (tau_marshall)	✅ scalars, fixed & variable arrays, nested datasets
XML configuration (tau_xml)	✅ datasets, telegrams, com-parameters
SDTv2 safety layer	❌ intentionally excluded

Application utilities (TAU)

Area	Status
Unified session (tlc_if) + statistics	✅
Train Topology Info (tau_tti)	✅ all 18 API fns (value-based wire parsing)
TCN-DNS (tau_dnr)	✅ uri↔addr, label resolution
ECSP control (tau_ctrl)	✅ set/get/confirm
Service interface (tau_so_if)	✅ add/del/upd/list
XML/comId marshalling (tau_xmarshall)	✅ marshal/unmarshal by comId
Session-from-XML (tau_xsession)	✅ publishers/subscribers per telegram
Indexed PD send timer (trdp_pdindex)	✅ optional, equivalence-tested

⚠️ Not safety-certified. The SDTv2 safety layer (IEC 61375-2-3 Annex B) is deliberately not ported. Do not use TRDP.NET to implement safety-related (SIL) functions. See NOTICE.

Validation

Validated live against the TCNOpen C reference (built locally): the reference sendHello publishes PD that TRDP.NET receives and decodes correctly (header, sequence, FCS). See the "Validation backlog" in PORTING.md. For wire-level inspection use Wireshark with the TRDP dissector (trdp/spy in TCNOpen).

License

Mozilla Public License 2.0 (MPL-2.0). TRDP.NET is a source-code translation of the MPL-2.0-licensed TCNOpen TRDP stack and therefore — as a derivative work — remains under MPL-2.0. Original copyright: Bombardier Transportation Inc. or its subsidiaries and others, 2013-2021. See LICENSE and NOTICE.

Not affiliated with or endorsed by TCNOpen, NewTec GmbH, or the IEC. "TRDP" and "TCNOpen" are used descriptively to identify the implemented protocol.

Build & test

dotnet test

Targets net8.0. No external runtime dependencies.

Repository layout

src/Trdp.Net/           # the library
  Vos/                  # platform abstraction (BCL-backed): CRC, types
  Core/                 # wire types: constants, PD/MD headers
tests/Trdp.Net.Tests/   # xUnit tests, validated against the original stack

Acknowledgements

This project would not exist without the TCNOpen initiative (hosted on SourceForge) and its contributors (notably Bernd Loehr, NewTec GmbH).