node-tcp-proxy

A classical TCP proxy that may be used to access a service on another network. An extensible replacement for socat when used thus

socat TCP-LISTEN:port,fork TCP:host:port

port is where socat listens for incoming requests. host:port are the host and port where the actual service is listening at.

To achieve the same with node-tcp-proxy

tcpproxy  --proxyPort port [--hostname <name or IP>] --serviceHost host1,host2 --servicePort port1,port2 [--q] [--tls [both]] [--pfx file] [--passphrase secret]

Optionally, use --hostname to specify host or IP address to listen at. Node.js listens on unspecified IPv6 address :: by default. If --serviceHost and --servicePort specify a comma separated list, the proxy will perform load balancing on a round-robin basis.

TLS can be enabled at the proxy port using --tls. Use --pfx followed by path to specify server certificate, and --passphrase to provide the password required to access it. Use --tls both, to also enable TLS with the service.

npm

Install node-tcp-proxy using npm

sudo npm install -g node-tcp-proxy

Programming Interface

To create a proxy in your own code

var proxy = require("node-tcp-proxy");
var newProxy = proxy.createProxy(8080, "host", 10080);

To end the proxy

newProxy.end();

hostname can be provided through an optional fourth parameter e.g. {hostname: 0.0.0.0} to createProxy. Console output may be silenced by adding quiet: true e.g. {hostname: 0.0.0.0, quiet: true}.

If you specify more than one service host and port pair, the proxy will perform round-robin load balancing

var hosts = ["host1", "host2"];
var ports = [10080, 10080];
var newProxy = proxy.createProxy(8080, hosts, ports);
// or var newProxy = proxy.createProxy(8080, "host1,host2", "10080,10080");

You can intercept and modify data sent in either direction, and modify the service host selection strategy

var proxy = require("node-tcp-proxy");
var util = require("util");
var serviceHosts = ["www.google.com", "www.bing.com"];
var servicePorts = [80, 80];
var newProxy = proxy.createProxy(8080, serviceHosts, servicePorts, {
    upstream: function(context, data) {
        console.log(util.format("Client %s:%s sent:",
            context.proxySocket.remoteAddress,
            context.proxySocket.remotePort));
        // do something with the data and return modified data
        return data;
    },
    downstream: function(context, data) {
        console.log(util.format("Service %s:%s sent:",
            context.serviceSocket.remoteAddress,
            context.serviceSocket.remotePort));
        // do something with the data and return modified data
        return data;
    },
    serviceHostSelected: function(proxySocket, i) {
        console.log(util.format("Service host %s:%s selected for client %s:%s.",
            serviceHosts[i],
            servicePorts[i],
            proxySocket.remoteAddress,
            proxySocket.remotePort));
        // use your own strategy to calculate i
        return i;
    }
});

Alternatives

You may want to check out these interesting alternatives

• http-proxy - programmable proxying library that supports websockets. It is suitable for implementing components such as reverse proxies and load balancers.

• sslh - accepts connections on specified ports, and forwards them further based on tests performed on the first data packet sent by the remote client.

• socat - socat is a relay for bidirectional data transfer between two independent data channels. Each of these data channels may be a file, pipe, device (serial line etc. or a pseudo terminal), a socket (UNIX, IP4, IP6 - raw, UDP, TCP), an SSL socket, proxy CONNECT connection, a file descriptor (stdin etc.), the GNU line editor (readline), a program, or a combination of two of these.