socket-test.js

const net = require('net');
let isConnected = false;
const delay = time => new Promise(resolve => setTimeout(resolve, time));

const client = net.createConnection({ host: '192.168.7.2', port: '9999' }, () => {
    console.log('client connected to machine motion');
    isConnected = true;
});

let count = 1;
client.on('data', (data) => {
    console.log(`received ${count}:`,data.toString() + '\n')
    count++;
});

client.on('error', () => console.log('error to connect to MM'));

(async function main() {
    while (!isConnected) {
	await delay(1000);
	console.log('isConnected: ', isConnected);
    }

    client.write('io-expander/1/digital-input/0');
    await delay(100);
    client.write('io-expander/1/digital-input/1');
    await delay(100);
    client.write('io-expander/1/digital-input/2');
    await delay(100);
    client.write('io-expander/1/digital-input/3');
    await delay(100);
    client.write('io-expander/1/digital-input/0');
    await delay(100);
    client.write('io-expander/1/digital-input/1');
    await delay(100);
    client.write('io-expander/1/digital-input/2');
    await delay(100);
    client.write('io-expander/1/digital-input/3');
    await delay(100);
    client.write('io-expander/1/digital-input/0');
    await delay(100);
    client.write('io-expander/1/digital-input/1');
    await delay(2000)
    client.write('io-expander/1/digital-output/0 1');
    await delay(1000);
    client.write('io-expander/1/digital-output/1 1');
    await delay(1000);
    client.write('io-expander/1/digital-output/2 1');
    await delay(1000);
    client.write('io-expander/1/digital-output/3 1');

    client.write('io-expander/1/digital-output/0 0');
    await delay(1000);
    client.write('io-expander/1/digital-output/1 0');
    await delay(1000);
    client.write('io-expander/1/digital-output/2 0');
    await delay(1000);
    client.write('io-expander/1/digital-output/3 0');
})()