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(buf, src, dst, out) {
	var evt = {
		"buf": buf,
		"src": src,
		"dst": dst,
		"out": out
	};
	var next = Proxy.nop;
	for(var i = this.mid.length - 1; i >= 0; i--) {
		next = this.mid[i].bind(this, evt, next);
	}
	next();
	return this;
};

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

// built-in middlewares

Proxy.nop = function() {
};

Proxy.send = function(evt, next) {
	evt.dst.write(evt.buf);
	next();
};

Proxy.consoleLogMeta = function(evt, next) {
	console.log(
		(evt.out ? "\x1B[35m" : "\x1B[33m")
		+ evt.src.remoteAddress + ":" + evt.src.remotePort
		+ "  ——>  "
		+ evt.dst.remoteAddress + ":" + evt.dst.remotePort
		+ " —— " + evt.buf.length + " bytes"
		+ "\x1B[0m"
	);
	next();
};

Proxy.consoleLogString = function(evt, next) {
	console.log(evt.buf.toString());
	next();
};

Proxy.consoleLogBuffer = function(evt, next) {
	var i = 0;
	while(i + 16 < evt.buf.length) {
		console.log(evt.buf.slice(i, i + 16));
		i += 16;
	}
	if(i < evt.buf.length) console.log(evt.buf.slice(i));
	next();
};

Proxy.consoleLogSnippet = function(evt, next) {
	var str = evt.buf.toString();
	var i;
	var ellip = false;
	i = str.indexOf("\n"); if(i != -1) {
		str = str.substr(0, i);
		ellip = true;
	}
	i = str.indexOf("\r"); if(i != -1) {
		str = str.substr(0, i);
		ellip = true;
	}
	var rows = 80; //process.binding('stdio').getRows();
	if(str.length > rows) {
		str = str.substr(0, rows);
		ellip = true;
	}
	if(ellip) {
		str += "…";
	}
	console.log(str);
	next();
};

module.exports = Proxy;


/* Usage:

var Proxy = require("./lib/proxy");

Proxy.to("test.com", 80)
.use(Proxy.consoleLogMeta)
.use(Proxy.send)
.listen(8080);

*/