node.js tcp proxy

proxy.js

var net = require("net");

var Proxy = function() {
};
Proxy.to = function(dst_host, dst_port) {
	var proxy = new Proxy();
	proxy.dstHost = dst_host;
	proxy.dstPort = dst_port;
	proxy.mid = [];
	return proxy;
};

Proxy.prototype.use = function(fn) {
	this.mid.push(fn);
	return this;
}

Proxy.prototype.handle = function(data, src, dst) {
	var next = Proxy.nop;
	for(var i = this.mid.length - 1; i >= 0; i--) {
		next = this.mid[i].bind(this, data, src, dst, next);
	}
	next();
	return this;
};

Proxy.prototype.listen = function(port) {
	var self = this;
	this.server = net.createServer(function (sockA) {
		var preb = [];
		sockA.on("data", pre = function(data) {
			preb.push(data);
		});
		var sockB = net.connect(self.dstPort, self.dstHost, function() {
			sockA.removeListener("data", pre);
			while(preb.length) {
				self.handle(preb.shift(), sockA, sockB);
			}
			sockA.on("data", function(data) {
				self.handle(data, sockA, sockB);
			});
			sockB.on("data", function(data) {
				self.handle(data, sockB, sockA);
			});
			sockA.on("end", function() {
				sockB.removeAllListeners();
				sockB.end();
			});
			sockB.on("end", function() {
				sockA.removeAllListeners();
				sockA.end();
			});
		});
	});
	this.server.listen(port, function() {
		// hello I am listening
	});
	return this;
};

// built-in middlewares

Proxy.nop = function() {
};

Proxy.send = function(data, src, dst, next) {
	dst.write(data);
	next();
};

Proxy.consoleLog = function(data, src, dst, next) {
	console.log(" … " + src.remoteAddress + ":" + src.remotePort + "  -->  " + dst.remoteAddress + ":" + dst.remotePort);
	console.log(data.toString());
	next();
};

////////////////////////////////

Proxy.to("www.bestbeer.com", 80).use(Proxy.consoleLog).use(Proxy.send).listen(8080);