Master Control Program
In order to control our SwarmBots, we need a way to process incoming user messages from Twitter, parse those messages, and then send the appropriate commands to the bots. This guide will go over the higher level concepts and control flow, but leave the implementation of some aspects, such as which commands to look for, to the developer.
Before we get started, we need to make sure our development environment is set up correctly. The first thing you should do is sign up as a developer on Twitter. Once you have signed up you can create a new Twitter application. Be sure to call it MySwarmBots or something else that clearly distinguishes it. Next you’ll need to save the aplication key and secret to your bash profile (if using Linux). Next you should sign up for a free instance from MongoLab. We will use this to store information that can be used to communicate with a web application. If you do not want to have a web application, and just want to be able to tweet at your SwarmBots, consider that database optional. Finally, be sure you have Node.js installed, as we will be writing our application in JavaScript.
Below is the list of dependencies that you will need. They can be installed through npm.
// Library for making authorized API requests.
var rem = require('rem');
// Used for processing data streams, in our case Twitter.
var carrier = require('carrier');
// Used for connecting to our remote database.
var MongoClient = require('mongodb').MongoClient;
// Used for connecting to our master Arduino over serial.
var serialport = require('serialport')
var SerialPort = serialport.SerialPort
var serialPort = new SerialPort("/dev/ttyACM0", {
baudrate: 9600,
parser: serialport.parsers.readline("\n")
}, false);
// Our custom interface to the database explained in the next post.
var mongo = require('./dbhelper');Once we have everything installed and set up, we can go ahead and get started designing our control flow. The first thing we will do is connect to our remote database. The rest of our program will run inside the callback to this function, so it will have access to the database.
// Start connection to MongoDB. Make sure your environment variables have been configured.
MongoClient.connect(process.env.SWARMBOTS_MONGO_URI, function (err, db){Next, we will use Rem.js to connect to twitter and open a stream. We want to configure the stream to filter out a keyword that we will listen for and intercept. For our purposes, we will be listening for the use of the word ‘SwarmBots.’ Everytime the stream finds a relevant tweet, it gets collected by our Carrier until the full text has been received. Then, we pass the tweet off into our control system.
// Create Twitter API, prompting for key/secret.
var tw = rem.connect('twitter.com', 1).configure({
'key': process.env.TW_SWARMBOTS_KEY,
'secret': process.env.TW_SWARMBOTS_SECRET
}).promptAuthentication(function (err, user){
user.stream('statuses/filter').get({'track': 'swarmbots'},function (err, stream) {
carrier.carry(stream, function (line){
if (line){
var line = JSON.parse(line);
parseTweet(line);
}
});
});The first step in our message’s journney is to be parsed for logistical information. Here we are just getting some basic user data so we can show who is using SwarmBots on our website. Then, se send the packaged information off to our command checker.
var parseTweet = function(json){
//console.log(json.id_str, json.text, json.user);
if (json.user.name != "SwarmBots"){
user_info= {sid:json.id_str, name:json.user.name, location:{name:json.user.location}, type:'tw',picture:{data:{url:json.user.profile_image_url}} }
//autoRespond(json.user.screen_name);
checkValidCommand(json.text, user_info, json.user.screen_name);
}
}He you can write your own custom code to look for any specific command and pass that off for submission. In this example, we will just pass commands straight through, and assign them to an arbitrary bot.
var checkValidCommand = function(text, user_info, screen_name){
text = text.toLowerCase();
var bot = "bot0";
if (isValid(text)){
submitCommand(bot, user_info)
acceptCommand(screen_name);
}
}
var isValid = function(command) {
//write your own validation here.
}Here our submission function pushes the new command to the database. In this instance, we are using a shared Queue, but you could just as easily have a separate queue for each one of your bots.
var submitCommand = function(bot, json){
mongo.getSwarmBot(db, bot, function (err, sb){
mongo.getQueue(db, function (err, queue){
if(queue.people.indexOf(json.sid) > -1){
declineDuplicate(json.user.screen_name);
}else{
queue.meta.push({name: json.name, photo: json.picture.data.url, location: json.location.name, sid:json.sid});
queue.people.push(json.sid);
//mongo.updateSwarmBot(db, sb, function (){
mongo.updateQueue(db, queue, function (){
});
//});
}
});
});
} The following is just an example of some reciept messages you can send to users, and how to send them.
// Create a queue of tweets to be sent out.
var tweetQueue =[];
var acceptCommand = function(screen_name){
sendReceipt(screen_name);
}
var sendReceipt = function(screen_name){
tweetQueue.push("@" + screen_name + " you have successfully moved our bots! Thanks!");
}
var declineDuplicate = function(screen_name){
tweetQueue.push("@" + screen_name + " sorry, you can only be in the queue once. Try again once your turn is up!");
}
var declineCommand = function(screen_name){
tweetQueue.push("@" + screen_name + " that is an invalid command.");
}
// How we actually send a tweet, using Rem.js.
var tweet = function(){
if (tweetQueue.length > 0){
user('statuses/update').post({
status: tweetQueue.shift()
}, function (err, json){
console.log("Tweet sent.");
});
}
}
// We need to rate limit our tweets to keep Twitter happy.
setInterval(tweet, 60000);Finally, we will get into sending and receiving messages with the master Arduino.
// Used to hold outgoing messages.
var dispatchQueue = [];
// Open a serial connection with our Arduino.
serialPort.open(function () {
// Listen for any returning messages, send them to the parser.
serialPort.on('data', function(data) {
parseMessage(data);
console.log(data);
});
var parseMessage = function(message){
if(message.indexOf('response:') > -1){
// If this is a response, get the message
// In this example, the message is encoded in the last 4 characters.
var resp = message.substring(message.length - 4, message.length)
if (resp != '0000'){
// If the bot is ready, get the next move and dispatch it.
getNextMove();
}
}
}
// Add he next move from the database to the local queue.
var getNextMove = function(){
mongo.getQueue(db, function (err, queue){
if (queue.length > 1){
dispatchQueue.push(queue.shift());
console.log(dispatchQueue);
}
mongo.updateQueue(db, queue, function (){
dispatch();
});
});
}
// Write the next message out to serial.
var dispatch = function(){
if(dispatchQueue.length > 0){
console.log("Writing to serial...");
message = dispatchQueue.shift()
serialPort.write(message);
}
}
});
});The full source code can be found on the SwarmBots GitHub page.