tcp.client

// body-parse is necessary for posting data
const express = require('express');
const bodyParser = require('body-parser');
const app = express();
const ejs = require('ejs');
const crc = require('crc');


// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({extended: false}));

const logger = require('morgan');
app.use(logger());
app.use('assets', express.static('public'));
app.engine('html', ejs.__express);
app.set('view engine', 'html');
// parse application/json
// app.use(bodyParser.json());

app.use(function (req, res, next) {
    console.log('Time: %f', Date.now());
    // res.write('home');
    next(); //!!!!!!!!! Important if you want to following request
});

app.get('/login', (req, res, next) => {
    res.render('form');
    next();
});

app.post('/login', (req, res, next) => {
    // res.setHeader('Content-Type', 'text/plain')
    let arr = [parseInt('fe', 16).toString(10)];
    if (req.body.commd.toString().length > 0) {
        arr.push(req.body.commd.toString());
    } else {
        arr.push('5');
    }
    if (req.body.path > 0) {
        arr.push('00');
        arr.push((req.body.path - 1).toString());
    } else {
        arr.push('00');
        arr.push('00');
    }
    if (!req.body.switch) {
        arr.push('00');
        arr.push('00');
    }
    else {
        arr.push('ff');
        arr.push('00');
    }
    let tempBuf = Buffer.from(arr);
    let buf = crc16Check(arr, tempBuf);
    // console.log('arr', arr);
    console.log('buf', buf);

    // res.end(JSON.stringify(req.body, null, 2));
    next();
});

function crc16Check(arr, buf) {
    let crcStr = crc.crc16modbus(buf).toString(16);
    arr.push(parseInt(crcStr.slice(crcStr.length - 2, crcStr.length), 16).toString(10));
    arr.push(parseInt(crcStr.substr(0, crcStr.length - 2), 16).toString(10));
    return Buffer.from(arr);
}

const PORT = 3005;
app.listen(PORT, (err) => {
    if (err) throw err
    else {
        console.log(`server listening to ${PORT}`)
    }
})