Eamorr Eamorr - 6 months ago 19
Node.js Question

Node.js - forward all traffic from port A to port B

I'm trying to forward all traffic from port 6999 to port 7000 (I know I could use iptables, but the idea is to use Node.js to do some packet inspection).

Here is the code I have sofar:

var net=require('net');
var compress=require('./node-compress/compress');

var ip='172.16.1.224';
var ipPort=6999;
var opPort=7000;

var output=net.createServer(function(connOut){
var input=net.createServer(function(connIn){
connIn.pipe(connOut);
});
input.listen(ipPort,ip);
});
output.listen(opPort,ip);


It just does not seem to work. When I do a tcpdump on port 7000, nothing shows up. Anyone have any suggestions?

Many thanks in advance,

Answer

Here's my go at it:

Supports giving the "from" and "to" from command line, and supports remote machines.

var net = require('net');

// parse "80" and "localhost:80" or even "42mEANINg-life.com:80"
var addrRegex = /^(([a-zA-Z\-\.0-9]+):)?(\d+)$/;

var addr = {
    from: addrRegex.exec(process.argv[2]),
    to: addrRegex.exec(process.argv[3])
};

if (!addr.from || !addr.to) {
    console.log('Usage: <from> <to>');
    return;
}

net.createServer(function(from) {
    var to = net.createConnection({
        host: addr.to[2],
        port: addr.to[3]
    });
    from.pipe(to);
    to.pipe(from);
}).listen(addr.from[3], addr.from[2]);

(save as proxy.js)

To forward from localhost:9001 => localhost:80

$ node proxy.js 9001 80

Or localhost:9001 => otherhost:80

$ node proxy.js 9001 otherhost:80

(This was based on Andrey's answer, thanks!)