bacnet-wasm

BACnet/SC thin client for JavaScript/TypeScript via WebAssembly.

Provides a browser-compatible BACnet/SC (Secure Connect) client that connects to BACnet/SC hubs over WebSocket. Built on the rusty-bacnet protocol stack.

The client starts BACnet/SC Heartbeat-Request/Heartbeat-ACK keep-alive handling after the Connect-Accept handshake.

The client enforces wss:// and BACnet/SC hub WebSocket framing, but browser trust stores and client certificate selection are controlled by the browser and platform. Annex AB mTLS conformance depends on that external certificate configuration.

Installation

npm install @rusty-bacnet/bacnet-wasm

Quick Start

import { BACnetScClient, ObjectTypes, PropertyIds, encodeReal } from '@rusty-bacnet/bacnet-wasm';

// Create client and connect to SC hub
const client = new BACnetScClient();
await client.connect('wss://hub.example.com:1234');

// Read a property
const value = await client.readProperty(
  ObjectTypes.analog_input(), // object type
  1,                          // instance number
  PropertyIds.present_value() // property identifier
);
console.log('Present Value:', value);

// Write a property
await client.writeProperty(
  ObjectTypes.analog_value(),
  1,
  PropertyIds.present_value(),
  encodeReal(72.5),  // application-tagged value bytes
  8                   // priority (optional)
);

// Subscribe to COV notifications
client.onCovNotification((data) => {
  console.log('COV notification:', data);
});
await client.subscribeCov(1, ObjectTypes.analog_input(), 1, true, 300);

// Send Who-Is
client.onIAm((data) => {
  console.log('I-Am received:', data);
});
client.whoIs();

// Disconnect
await client.disconnect();

API Reference

BACnetScClient

| Method | Description | |--------|-------------| | new() | Create a new client with secure random VMAC and generated Device UUID | | withDeviceUuid(deviceUuid) | Create a new client with secure random VMAC and a supplied persistent Device UUID | | connect(url) | Connect to SC hub via WebSocket | | readProperty(objectType, instance, propertyId, arrayIndex?) | Read a property | | writeProperty(objectType, instance, propertyId, valueBytes, priority?) | Write a property | | whoIs(low?, high?) | Send Who-Is broadcast | | subscribeCov(processId, objectType, instance, confirmed, lifetime?) | Subscribe to COV | | onIAm(callback) | Register I-Am callback | | onCovNotification(callback) | Register COV notification callback | | disconnect() | Disconnect from hub | | connected | Property: connection status | | localDeviceUuid | Property: local 16-byte Device UUID |

Value Encoding Helpers

| Function | Description | |----------|-------------| | encodeReal(value) | Encode a float as BACnet Real | | encodeUnsigned(value) | Encode an unsigned integer | | encodeBoolean(value) | Encode a boolean | | encodeEnumerated(value) | Encode an enumerated value |

Type Constants

• ObjectTypes — BACnet object type constants (e.g., analog_input(), device())
• PropertyIds — Property identifier constants (e.g., present_value(), object_name())

Architecture

This crate compiles the core BACnet protocol logic (types, encoding, services) to WebAssembly and bridges to the browser's native WebSocket API. BACnet/SC already uses WebSocket as its transport, making browsers a natural fit.

┌─────────────────────────┐
│  JavaScript/TypeScript   │
├─────────────────────────┤
│  BACnetScClient (WASM)  │
├──────────┬──────────────┤
│ SC Frame │  APDU/NPDU   │
│  Codec   │   Codec      │
├──────────┴──────────────┤
│  Browser WebSocket API  │
└─────────────────────────┘

License

MIT