FluentModbus.Secure 5.2.0-preview

FluentModbus

FluentModbus is a .NET Standard library (2.0 and 2.1) that provides Modbus TCP/RTU server and client implementations for easy process data exchange. Both, the server and the client, implement class 0, class 1 and class 2 (partially) functions of the specification. Namely, these are:

Class 0:

• FC03: ReadHoldingRegisters
• FC16: WriteMultipleRegisters

Class 1:

• FC01: ReadCoils
• FC02: ReadDiscreteInputs
• FC04: ReadInputRegisters
• FC05: WriteSingleCoil
• FC06: WriteSingleRegister

Class 2:

• FC15: WriteMultipleCoils
• FC23: ReadWriteMultipleRegisters

Modbus/TCP Security (mbaps)

⚠️ Development project — not production-tested. This feature is a work in progress. It has unit tests and a working sample, but it has not been tested or audited for production use. Nutzung auf eigenes Risiko / use at your own risk.

This fork adds support for Modbus/TCP Security — TLS-secured Modbus TCP with mutual X.509 certificate authentication and certificate-role-based authorization, as defined by the Modbus Organization (default port 802, TLS 1.2+). It is available on netstandard2.1 and net8.0.

A short bilingual (English/German) usage guide is in doc/secure-modbus-guide.md.

// server
using var server = new ModbusTcpServer();

server.StartSecure(new IPEndPoint(IPAddress.Any, 802), new ModbusTcpServerSecurityOptions
{
    Certificate = serverCertificate,                                      // incl. private key
    TrustedRootCertificates = new X509Certificate2Collection { rootCa },  // trusted client CA(s)
    Authorize = ctx => ctx.Role == "operator" || IsReadFunction(ctx.FunctionCode)
});

// client
using var client = new ModbusTcpClient();

client.Connect("192.168.0.1:802", new ModbusTcpClientSecurityOptions
{
    Certificate = clientCertificate,                                     // carries the role extension
    TrustedRootCertificates = new X509Certificate2Collection { rootCa }
});

The client's authorization role is carried in an X.509 certificate extension (OID 1.3.6.1.4.1.50316.802.1); use ModbusRoleCertificate.CreateRoleExtension(role) when issuing client certificates. See sample/SampleServerClientTcpSecure for a complete runnable example.

Please see the introduction to get a more detailed description on how to use this library!

Below is a screenshot of the sample console output using a Modbus TCP server and client: