Can't Connect To A Telnet Server From Node.js

Question

I have a telnet server embedded in a C++ app that I can connect to with no problem using telnet.

I want to write a node application that will connect to my server and I have tried this

var net = require('net');

var port = 6502
var host = '127.0.0.1'

var socket = net.connect(port,host, function() {
    console.log("Sending data");
    socket.write("hello\r\n")

    socket.on("data", function (data) {
        console.log("received data");
        console.log( data.toString() );
        socket.end();
    })
})

socket.on("error", function(err) {
    console.log("Error");
    console.log(err);
})

Unfortunately what I get back is this

> node test.js
{ [Error: connect ECONNREFUSED]
  code: 'ECONNREFUSED',
  errno: 'ECONNREFUSED',
  syscall: 'connect' }

What's really odd is if I set up a simple echo server with node everything works fine. Here's the working echo server code:

var net = require('net');

var server = net.createServer(function (socket) {
  socket.write('Echo server\r\n');
  socket.pipe(socket);
});

server.listen(6502, '127.0.0.1');

and from that I get

Sending data
received data
Echo server
hello

Is there any reason why:

• I can telnet into my app fine
• I can connect from node to my node echo server on the same port
• I get a connection refused if I connect from my node app to my app

Extra Info

• On OSX (mavericks)
• Node version 0.10.28
• Telnet server in C++ is provided via embedded lua and luasocket (lua 5.1)

Answer 1

Solved!

The issue is the code in my app server was binding to localhost and by default that binds to the IPV6 address of ::1

Passing a host of localhost to net.connect assumes IPV4 and doesn't work.

The mac command line telnet and nc both work fine with this and connect correctly.

Two solutions:

• App binds to 127.0.0.1 and localhost in node works fine
• Set host address to ::1 in test.js and it connects via ipv6

All fixed now though :)

gaz

Answer 2

Looks like you forgot to tell the server to listen in your code. It throws a connection refused error because there is nothing to connect to...

Add this at the end: server.listen(port);

Answer 3

The prototype for net.connect is (options, callback) See http://nodejs.org/api/net.html#net_net_connect_options_connectionlistener

I would then suggest to test your code against a standard telnet server to see how it behaves, and finally I would strongly recommend the use of jshint or jslint.