@signalk/streams/udp.js

Utilities for handling streams of Signal K data

/*
 * Copyright 2015 Teppo Kurki <teppo.kurki@iki.fi>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0

 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* Usage: This pipeElement takes any TCP stream and passes it to the next pipeElement.
 * It takes the options "host" and "port" and optionally "reconnect" (default true) and "maxRetries" (default 10)
 * Example:

 {
   "type": "providers/udp",
   "options": {
     "port": 12345
   },
   "optionMappings": [
     {
       "fromAppProperty": "argv.udpport",
       "toOption": "port"
     }
   ]
 },

 */

const Transform = require('stream').Transform

function Udp(options) {
  Transform.call(this, {
    objectMode: false
  })
  this.options = options
  this.debug = (options.createDebug || require('debug'))('signalk:streams:udp')
  this.debugData = (options.createDebug || require('debug'))(
    'signalk:streams:udp-data'
  )
}

require('util').inherits(Udp, Transform)

Udp.prototype.pipe = function (pipeTo) {
  this.pipeTo = pipeTo
  Udp.super_.prototype.pipe.call(this, pipeTo)

  const socket = require('dgram').createSocket('udp4')
  const self = this

  if (this.options.outEvent && this.options.port !== undefined) {
    this.options.app.on(this.options.outEvent, function (d) {
      self.debug('sending over udp: %s', d)
      socket.send(d, 0, d.length, self.options.port, '255.255.255.255')
    })
  }

  socket.on('message', function (message) {
    self.debug(message.toString())
    self.push(message)
  })
  socket.bind(this.options.port, function () {
    socket.setBroadcast(true)
  })
}

Udp.prototype._transform = function (chunk, encoding, done) {
  done()
}

Udp.prototype.end = function () {
  this.socket.close()
  this.pipeTo.end()
}

module.exports = Udp