API Reference

ModbusClient

The main entry point for Modbus TCP communication.

public sealed class ModbusClient : IDisposable
{
    ModbusClient(ActorSystem system, ModbusClientOptions options)

    bool IsConnected { get; }
    event Action? Disconnected;

    void Connect()
    void Dispose()

    Task<ushort[]> ReadAsync(ushort address, ushort count, bool inputRegister = false)
    Task WriteAsync(ushort address, params ushort[] values)
}

Method	Description
Connect()	Creates the stream owner actor and TCP connection
ReadAsync	Reads holding registers (FC3) or input registers (FC4)
WriteAsync	Writes single (FC6) or multiple (FC16) registers
Dispose()	Stops the stream owner actor and cleans up

ModbusClientOptions

public sealed record ModbusClientOptions
{
    required string Host { get; init; }
    int Port { get; init; }             // default: 502
    byte UnitId { get; init; }          // default: 1
    TimeSpan Timeout { get; init; }     // default: 5s
    int QueueSize { get; init; }        // default: 256
}

Poll Extension

public static Source<RegisterResponse, UniqueKillSwitch> Poll(
    this ModbusClient client,
    TimeSpan interval,
    Action<PollBuilder> configure)

PollBuilder

public sealed class PollBuilder
{
    PollBuilder Registers(ushort address, ushort count, bool inputRegister = false)
}

Types

public sealed record ReadRequest(ushort Address, ushort Count, bool InputRegister = false);
public sealed record WriteRequest(ushort Address, ushort[] Values);
public sealed record RegisterResponse(ushort Address, ushort[] Registers);

public interface IWithModbusAddress
{
    ushort Address { get; }
}

ModbusCodec

public static class ModbusCodec
{
    // Pre-wired read flow connected to a device
    static Flow<ReadRequest, RegisterResponse, NotUsed> ReadFlow(
        ActorSystem system, string host, int port, byte unitId = 1)
}

ModbusException

public sealed class ModbusException : Exception
{
    byte FunctionCode { get; }
    byte ErrorCode { get; }
}

Error Code	Meaning
1	Illegal Function
2	Illegal Data Address
3	Illegal Data Value
4	Slave Device Failure