Node.js: Basic TCP Client (à la Netcat) with Net and Readline Modules?

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Monocycle-ing Linguiste

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May 20, 2016, 4:42:49 PM5/20/16

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I'm not sure if it's bad form to repost my question from another site, but here goes:

My problem in short involves trying to build a very simple TCP client (think Netcat) with node's net module. I have had success with sock.write('GET etc...), but when I try to use the readline module to dynamically send data, the servers I have tried to talk to either never respond, or don't respond how I would expect them to.

My suspicion is that the readline module is escaping escape characters such as \r\n, which causes my request to the servers to be improperly formatted. I have tried:

client.write(new Buffer(cmd))

But my basic TCP server is still interpreting /r/n as text. In fact, the native console interprets it as text.

Update: I have verified by using JSON.stringify on the terminal output that something is escaping escape characters (e.g. When I enter \r\n into the terminal the JSON.stringify -ed terminal input reads as \\r\\n). Maybe my terminal is doing it by default and this isn't at all a problem with node.js? I'm using Windows Powershell.

See my client script below for further clarification:

// Inspired and sourced from: http://www.hacksparrow.com/tcp-socket-programming-in-node-js.html

// ANSI escape code sequence for colors, etc. General Form: "\x1b[Nm" Where N is a number.

// For http requests, see http://stackoverflow.com/questions/6686261/what-at-the-bare-minimum-is-required-for-an-http-request

//For IRC protocol see https://news.ycombinator.com/item?id=2071318

var net = require('net');
var fs = require('fs');
var readline = require('readline');


var host = 'localhost';
var port = 6667;

var client = new net.Socket();
client.connect(port, host, function() {

    console.log('CONNECTED TO: ' + host + ':' + port + '\n');
    // Write a message to the socket as soon as the client is connected, the server will receive it as message from the client 
    client.write('USER foo bar batz boo\r\nNICK test345\r\n');
//    client.write('JOIN #mae\r\n');

  rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
  });

  rl.on('line', function(cmd) {
    var bufferCommand = new Buffer(cmd)
    console.log('bufferCommand = ' + bufferCommand);
    client.write(bufferCommand);
  });

});



// Add a 'data' event handler for the client socket
// data is what the server sent to this socket
client.on('data', function(data) {


    console.log('DATA: ' + data);

    var fs = require('fs');


    fs.appendFile("log.txt", data, function(err) {

      if(err) {
        return console.log(err);
      }

      console.log("The file was saved!");
    }); 

});

// Catches error if no TCP server to answer request.
client.on('error', function(error) {
  console.log(error);
});

// Add a 'close' event handler for the client socket
client.on('close', function() {
    console.log('Connection closed');
});