@modbus-ts/client

High-level Modbus client API for read, write, and subscribe.

Installation

pnpm add @modbus-ts/client

Core Exports

• ModbusClient
• ModbusClientOptions
• ClientEvent

Minimal Example

import { ModbusClient } from '@modbus-ts/client'
import { TcpTransport } from '@modbus-ts/transport-tcp'

const client = new ModbusClient({
  transport: new TcpTransport({ host: '127.0.0.1', port: 502 }),
  defaultUnitId: 1,
  defaultTimeout: 1000,
  mode: 'tcp',
})

await client.connect()
const regs = await client.readHoldingRegisters(0, 4)
const inputRegs = await client.readInputRegisters(0, 4)
const coils = await client.readCoils(0, 8)
const discreteInputs = await client.readDiscreteInputs(0, 8)

await client.writeMultipleRegisters(10, [1, 2, 3, 4])
await client.writeSingleCoil(11, true)
await client.writeMultipleCoils(12, [true, false, true])

console.log({ regs, inputRegs, coils, discreteInputs })
await client.close()

Events

• connect
• disconnect
• timeout
• error

Point Mapping

| Point Type | Function Code | Read API | Write API | | ----------------- | ------------- | -------------------- | -------------------------------------------- | | Coils | FC1/FC5/FC15 | readCoils | writeSingleCoil / writeMultipleCoils | | Discrete Inputs | FC2 | readDiscreteInputs | Not supported by Modbus spec | | Holding Registers | FC3/FC6/FC16 | readHoldingRegisters | writeSingleRegister / writeMultipleRegisters | | Input Registers | FC4 | readInputRegisters | Not supported by Modbus spec |

API Selection Guide

• Use readCoils for digital output status bits.
• Use readDiscreteInputs for read-only digital input bits.
• Use readHoldingRegisters for writable word registers.
• Use readInputRegisters for read-only word registers.

Packages

• high-level Modbus client
• shared contracts, types, and errors
• FC1/FC2/FC3/FC4/FC5/FC6/FC15/FC16 frame encode/decode for TCP/RTU/ASCII
• serial request queue with priority
• polling engine and range merge
• Node TCP transport with reconnect
• Node UDP transport
• browser WebSocket transport with reconnect
• typed Electron main/renderer bridge
• Electron IPC transport adapter
• WebSocket to TCP binary relay gateway
• register-value codec helpers
• shared async and comparison utilities