NGCP Communication for JavaScript

Introduction

NGCP's communication framework for JSON-based communication in Node.js JavaScript framework.

npm install ngcp-communication-js

Messenger class

This package includes the Messenger class to send and receive messages to other vehicles using the JSON communication system. You can create an instance of the Messenger class by doing the following:

import { Messenger } from 'ngcp-communication-js';

const MY_PORT = 'PORT';
const MY_VEHICLE_ID = 0;

const messenger = new Messenger(MY_PORT, MY_VEHICLE_ID);

Receiving messages

You can attach callbacks to the instance that are invoked whenever you receive a message/object or when a vehicle disconnects (fails to send a message within a certain amount of time).

messenger.onStartMessage = (message) => {
  // ...
};

The following are the callbacks you can use:

• messenger.onConnectionAcknowledgementMessage(message)

  • Invoked when you receive a connection acknowledgement message

• messenger.onStartMessage(message)

  • Invoked when you receive a start message

• messenger.onAddMissionMessage(message)

  • Invoked when you receive an add mission message

• messenger.onPauseMessage(message)

  • Invoked when you receive a pause message

• messenger.onResumeMessage(message)

  • Invoked when you receive a resume message

• messenger.onStopMessage(message)

  • Invoked when you receive a stop message

• messenger.onUpdateMessage(message)

  • Invoked when you receive an update message

• messenger.onPOIMessage(message)

  • Invoked when you receive a point of interest (POI) message

• messenger.onCompleteMessage(message)

  • Invoked when you receive a complete message

• messenger.onConnectMessage(message)

  • Invoked when you receive a connect message

• messenger.onBadMessage(message)

  • Invoked when you receive a bad message

• messenger.onReceiveInvalidObject(object)

  • Invoked when you receive an object that is not a message. The object is not undefined and is not null. It will always be at least an empty object {}.

Vehicle disconnection

There is a callback that is invoked whenever a vehicle disconnects from you:

• messenger.onVehicleDisconnect(vehicleId)
  • vehicleId is the ID of the disconnected vehicle

Sending messages

You can also call functions to send messages. They all require the vehicle ID of the vehicle you are sending the message to, as well as extra information if the message requires it.

const TARGET_VEHICLE_ID = 100;
const ISR_SEARCH_JOB_TYPE = 'isrSearch';

messenger.sendStartMessage(TARGET_VEHICLE_ID, ISR_SEARCH_JOB_TYPE)

The following are all the functions you can call:

• messenger.sendConnectionAcknowledgementMessage(targetVehicleId)

• messenger.sendStartMessage(targetVehicleId, jobType)

• messenger.sendAddMissionMessage(targetVehicleId, task)

• sendPauseMessage(targetVehicleId)

• sendResumeMessage(targetVehicleId)

• sendStopMessage(targetVehicleId)

• sendUpdateMessage(targetVehicleId, lat, lng, status, extras)

  • extras is an object containing alt, heading, battery, and errorMessage which are all optional fields for an update message

• sendPOIMessage(targetVehicleId, lat, lng)

• sendCompleteMessage(targetVehicleId)

• sendConnectMessage(targetVehicleId, jobsAvailable)

All types for the messages are defined in the wiki here.

All types for the jobs and tasks are defined in the wiki here.

UpdateHandler class

This package also includes the UpdateHandler class to asynchronously listen to events and have callbacks:

import { UpdateHandler } from 'ngcp-communication-js';

const updateHandler = new UpdateHandler();

const EXPIRATION_TIME_MS = 1000; // 1 second

// function to call if an event happens for this handler
function onEvent(value, options) {
}

// function to call if event should remove this handler
function shouldRemove(value, options) {
}

// function to call if this handler expires (this is optional)
function onExpire() {
}

// the expiration time and onExpire arguments are completely optional
updateHandler.addHandler('yourEventName', onEvent, shouldRemove, EXPIRATION_TIME_MS, onExpire);

const value = ''; // can be any value
const options = { something: 10 };

// you can call this function to invoke an event
updateHandler.processEvent('yourEventName', value, options);

Other features

Config

This package has static configurations included with it that you can use:

import { Config } from 'ngcp-communication-config'

const { disconnectionTimeMs, messageSendRateMs, vehicles } = Config;

• disconnectionTimeMs: amount of time (in milliseconds) before a vehicle disconnects if it receives no messages from the other

• messageSendRateMs: amount of time message is sent again if it is not acknowledged yet (not all messages require acknowledgement so this does not apply to all messages)

• vehicles: mapping of vehicle ID to vehicle information, which includes:

  • macAddress: MAC address of the vehicle
  • name: name of the vehicle
  • type: type of vehicle, either station, plane, or rover

TypeScript support

This package includes TypeScript typings for any TypeScript projects:

import { Message, Task } from 'ngcp-communication-js';

const pauseMessage: Message.PauseMessage = { type: 'pause' };

const loiterTask: Task.LoiterTask = {
  taskType: 'loiter',
  lat: 14.54321812347,
  lng: 5.453286523,
  alt: 50.254387612,
  radius: 3.5634923,
  direction: 0
}

License

MIT