Writing a very simple IRC bot in Node.js

So there a few crap IRC bot libraries for Node.js out there, one of which I am using for my IRC client, although I may change to this cos it's so easy. I decided to see how easy it would be to write my own, and it's... really easy!

We will be using the net module, specifically net.Socket.

The basic bot

The extremely extremely basic IRC bot: (does not respond to ping)

var net = require('net');
var irc = {};

irc.socket = new net.Socket();
irc.socket.on('connect', function () {
	console.log('Established connection, registering and shit...');
	setTimeout(function () {
		irc.raw('NICK nick');
		irc.raw('USER callum 8 * :Node.js IRC bot');
	}, 1000);
});

irc.socket.setEncoding('ascii');
irc.socket.setNoDelay();
irc.socket.connect(6667, 'irc.freenode.net');

That's it. That code will connect to freenode under the nick "nick", idle for a couple minutes, and time out.

We want it to do something though, so we will add "listeners" to make it easy and avoid core code edits:

irc.socket.on('data', function (data) {
	data = data.split('\n');
	for (var i = 0; i < data.length; i++) {
		console.log('RECV -', data[i]);
		if (data !== '') {
			irc.handle(data[i].slice(0, -1));
		}
	}
});

//handles incoming messages
irc.handle = function (data) {
	var i, info;
	for (i = 0; i < irc.listeners.length; i++) {
		info = irc.listeners[i][0].exec(data);
		if (info) {
			irc.listeners[i][1](info, data);
			if (irc.listeners[i][2]) {
				irc.listeners.splice(i, 1);
			}
		}
	}
};

irc.listeners = [];
irc.on = function (data, callback) {
	irc.listeners.push([data, callback, false])
};
irc.on_once = function (data, callback) {
	irc.listeners.push([data, callback, true]);
};

This is fairly simple: use

irc.on

with a regex and a callback, and when the regex matches something, the callback is called.

irc.on_once

is similar, but it'll only be called once - good for something like joining a channel and setting a callback to send a message when we have joined the channel, instead of hoping you're on a fast connection and risking a 404 error. We'll also add an

irc.raw

method, because we're too lazy to send everything manually:

irc.raw = function (data) {
	irc.socket.write(data + '\n', 'ascii', function () {
		console.log('SENT -', data);
	});
};

That writes the data to the socket, and then when it has been written logs it to console.

This is how you tell it to respond to ping:

irc.on(/^PING :(.+)$/i, function (info) {
	irc.raw('PONG :' + info[1]);
});

I said it was easy ;-)

The full code is here: https://gist.github.com/996827. The full code also contains configuration and automatic channel joining on connect, which is fairly self explanatory.

Additional features

Here are a few extra things you may wish to add:

Nick changes
When the bot's nick changes, it updates

irc.nick

. This can be handy for other things, including a few methods I'll be putting below this one.

	irc.on(/^[^ ]+ 001 ([0-9a-zA-Z\[\]\\`_\^{|}\-]+) :/, function (info) {
		irc.nick = info[1];
	});
	irc.on(/^:([^!]+)![^@]+@[^ ]+ NICK :(.+)$/, function (info) {
		if (info[1] === irc.nick) {
			irc.nick = info[2];
		}
	});

Join channel
This is fairly self explanatory, but just demonstrates how you can use

irc.on_once

for callbacks.

irc.join = function (chan, callback) {
	if (callback !== undefined) {
		irc.on_once(new RegExp('^:' + irc.info.nick + '![^@]+@[^ ]+ JOIN :' + chan), callback);
	}
	irc.info.names[chan] = {};
	irc.raw('JOIN ' + chan);
};

(Yeah I know, my regex for that one sucks. But it works.)

Send message to channel
This code splits the message into nicely sized chunks, and then sends them.

irc.msg = function (chan, msg) {
	var max_length, msgs, interval;
	max_length = 500 - chan.length;

	msgs =  msg.match(new RegExp('.{1,' + max_length + '}', 'g'));

	interval = setInterval(function () {
		irc.raw('PRIVMSG ' + chan + ' :' + msgs[0]);
		msgs.splice(0, 1);
		if (msgs.length === 0) {
			clearInterval(interval);
		}
	}, 1000);
};

Kick / ban from channel
I think this is the only complicated piece of code in the entire thing.

irc.kick

without ban specified is boring and just kicks the user, but with ban specified, it sends the ban command, waits for it to be executed, and then kicks the user, too.

irc.kick = function (nick, chan, msg, ban) {
	if (ban !== undefined) {
		irc.ban(nick, chan, function () {
			irc.kick(nick, chan, msg);
		});
		return;
	}
	irc.raw('KICK ' + chan + ' ' + nick + ((msg !== undefined) ? ' :' + msg : ''));
};

irc.ban = function (nick, chan, callback) {
	var host, regex;
	if (irc.info.names[chan][nick] === undefined) {
		return false;
	}
	host = irc.info.names[chan][nick].host;
	regex = '^:' + irc.info.nick + '![^@]+@[^ ]+ MODE ' + chan + ' \\+b \\*!\\*@' + host;

	if (callback !== undefined) {
		irc.on_once(new RegExp(regex), function () {
			callback();
		});
	}
	irc.raw('MODE ' + chan + ' +b *!*@' + host);
};

Remember: when in doubt, consult RFC 1459! (cmd+f is your friend)

Two (sort of three) corrections:

irc.socket.on: When you check for the empty string, I think you mean data[i], not data. And why are you calling handle with

data[i].slice(0, -1)

? This will chop off the last character of data[i]. Perhaps you thought the '\n' would be left on there from split, but it isn't, so you really are just slicing off the last character of everything. (Am I wrong?)

irc.socket.handle: After the

irc.listeners.splice(i, 1);

you need

i--;

- otherwise your loop will skip the next listener.

I wrote a test case which combines both of the above mistakes as proof: http://jsfiddle.net/Y7yhr/

Also, lines in IRC are terminated by \r\n, not just \n. All of your data strings have \r at the end of them. This can be okay if you're okay with it though; your current implementation probably works fine.

Overall I like this tutorial though! Thanks.

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