led-bot/lights/request.js

import * as net from 'net';

const hostname = '192.168.1.219';
const port = 29999;

function getBinarySize(string) {
	return Buffer.byteLength(string, 'utf8');
}

function padLeft(size = 4, str = '') {
	let remaining = size - str.length;
	return '0'.repeat(remaining) + str;
}

export default function req(data, callback, errorCallback) {
	let string_data = JSON.stringify(data);
	let size = getBinarySize(string_data);
  if (size > 9999) {
    errorCallback("too long");
    return;
  }

	let client = new net.Socket();
	client.connect(port, hostname, () => {
		let res = client.write(padLeft(4, `${size}`));

		if (res) {
			client.write(string_data);
		}
		client.destroy();
		callback('success.');
	});

	client.on('error', (e) => {
		client.destroy();
		errorCallback(e);
	});
}