mastermind.js

const net = require('net');
const _ = require('lodash');

const state = [1, 1, 1, 1];

let index = 0;

var client = new net.Socket();

function makeGuess() {
    const currentGuess = getNextGuess().join('');
    console.log(`Guessing ${currentGuess}`);
    client.write(`GUESS ${currentGuess}\n`);
}

client.connect(18811, '0.tcp.ngrok.io', function() {
    client.write('START\n');
});

function getNextGuess() {
    let s = _.clone(state);

    if (state[index] < 7) {
        state[index]++;
    }

    if (state[index] === 6) {
        index++;
    }

    return s;
}

client.on('data', function(data) {
    const res = data.toString();
    console.log(`Got back ${res}`);

    if (_.startsWith(res, 'OK')) {
        makeGuess();
    } else {
        const a = _.toNumber(res.split(' ')[0]);
        console.log(a);
        // Make some changes
        makeGuess();
    }
});

client.on('close', function() {
    console.log('Connection closed');
});