Code.js

Minecraft.BetaClient = function(args) {
    	if(Minecraft.ENVIRONMENT == 'node') {
    		if(typeof Minecraft.node.net == 'undefined') Minecraft.node.net = require('net');
    		
    		this.host = args.host;
    		this.port = args.port || 25565;
    		this.username = args.username || 'Player';
    		this.status = 0;
    		
    		if(typeof args.onLogin == 'function') this.onLogin = args.onLogin;
    		
    		this.socket = new Minecraft.node.net.Socket();
    		this.socket.on('data', function(data) {
    			console.log(data);
    		}).connect(this.port, this.host, function() {
    			this.socket.write('\2' + args.username);
    			this.status = 1;
    		});
    		
    	} else {
    		throw new Error('Only compatible in node');
    	}
    };

Error

TypeError: undefined is not a function
    at repl:1:9
    at REPLServer.eval (repl.js:80:21)
    at repl.js:190:20
    at REPLServer.eval (repl.js:87:5)
    at Interface.<anonymous> (repl.js:182:12)
    at Interface.emit (events.js:67:17)
    at Interface._onLine (readline.js:162:10)
    at Interface._line (readline.js:426:8)
    at Interface._ttyWrite (readline.js:603:14)
    at ReadStream.<anonymous> (readline.js:82:12)