coap-server.js

const coap = require('coap')
const EventEmitter = require('eventemitter3')

const COAP_MULTICAST_ADDRESS = '224.0.1.187'
const GLOBAL_DEVID = '3332'
const STATUS_VALIDITY = '3412'
const STATUS_SERIAL = '3420'

const getDeviceIdentifier = device => `${device.type}#${device.id}#1`

const setUriPath = (res, uri) => {
  const parts = uri.split('/')
  const buffers = []

  for (const p of parts) {
    if (p) {
      buffers.push(Buffer.from(p))
    }
  }

  if (buffers.length > 0) {
    res.setOption('Uri-Path', buffers)
  }
}

class CoapServer extends EventEmitter {
  static registerOptions() {
    if (CoapServer._optionsRegistered) {
      return
    }

    coap.registerOption(
      GLOBAL_DEVID,
      str => Buffer.from(str),
      buf => buf.toString()
    )

    coap.registerOption(
      STATUS_VALIDITY,
      str => {
        const buf = Buffer.alloc(2)
        buf.writeUInt16BE(parseInt(str), 0)
        return buf
      },
      buf => buf.readUInt16BE(0)
    )

    coap.registerOption(
      STATUS_SERIAL,
      str => {
        const buf = Buffer.alloc(2)
        buf.writeUInt16BE(parseInt(str), 0)
        return buf
      },
      buf => buf.readUInt16BE(0)
    )

    CoapServer._optionsRegistered = true
  }

  constructor(device) {
    super()

    this.device = device
    this.server = null
    this.multicastServer = null
    this._serial = 1
    this._statusBroadcastTimeout = null

    this._boundRequestHandler = this._requestHandler.bind(this)

    CoapServer.registerOptions()
  }

  start() {
    this.device.on('change', this._deviceChangeHandler, this)

    return Promise.all([
      this._startServer(),
      this._startMulticastServer(),
    ])
      .then(() => {
        this._broadcastStatus()
      })
      .catch(error => {
        this.stop()
        throw error
      })
  }

  _startServer() {
    if (this.server !== null) {
      return Promise.resolve()
    }

    return new Promise((resolve, reject) => {
      this.server = coap.createServer()
        .on('request', this._boundRequestHandler)
        .listen(error => {
          if (!error) {
            resolve()
          } else {
            reject(error)
          }
        })
    })
  }

  _startMulticastServer() {
    if (this.multicastServer !== null) {
      return Promise.resolve()
    }

    return new Promise((resolve, reject) => {
      this.multicastServer = coap.createServer({
        multicastAddress: COAP_MULTICAST_ADDRESS,
      })
        .on('request', this._boundRequestHandler)
        .listen(error => {
          if (!error) {
            resolve()
          } else {
            reject(error)
          }
        })
    })
  }

  stop() {
    this.device.removeListener('change', this._deviceChangeHandler, this)

    if (this.server !== null) {
      this.server.close()
      this.server.removeListener('request', this._boundRequestHandler)
      this.server = null
    }

    if (this.multicastServer !== null) {
      this.multicastServer.close()
      this.multicastServer.removeListener('request', this._boundRequestHandler)
      this.multicastServer = null
    }

    if (this._statusBroadcastTimeout !== null) {
      clearTimeout(this._statusBroadcastTimeout)
      this._statusBroadcastTimeout = null
    }
  }

  _broadcastStatus() {
    if (this._statusBroadcastTimeout !== null) {
      clearTimeout(this._statusBroadcastTimeout)
    }

    this._statusBroadcastTimeout = setTimeout(
      this._broadcastStatus.bind(this),
      30000
    )

    const req = coap.request({
      host: COAP_MULTICAST_ADDRESS,
      pathname: '/cit/s',
      options: {
        [GLOBAL_DEVID]: getDeviceIdentifier(this.device),
        [STATUS_VALIDITY]: 38400,
        [STATUS_SERIAL]: this._serial++,
      },
      multicast: true,
      multicastTimeout: 100,
    })
    req.statusCode = '0.30'
    req.end(JSON.stringify(this.device.getCoapStatusPayload()))
  }

  _deviceChangeHandler() {
    this._broadcastStatus()
  }

  _requestHandler(req, res) {
    try {
      if (req.method === 'GET' && req.url === '/cit/s') {
        this._handleStatusRequest(req, res)
      }
    } catch (e) {
      console.error(e)
      throw e
    }
  }

  _handleStatusRequest(req, res) {
    console.log('GET /cit/s')

    setUriPath(res, '/cit/s')
    res.setOption(GLOBAL_DEVID, getDeviceIdentifier(this.device))
    res.setOption(STATUS_VALIDITY, 38400)
    res.setOption(STATUS_SERIAL, this._serial++)
    res.end(JSON.stringify(this.device.getCoapStatusPayload()))
  }
}

module.exports = CoapServer