server.js

var net = require('net');
const exec = require('child_process').exec;

var client = new net.Socket();
client.connect(1337, '127.0.0.1', function() {
	console.log('Connected');
	client.write('Hello, server! Love, Client.');
});

client.on('data', function(data) {
	console.log('Received: ' + data);
	client.destroy(); // kill client after server's response
});

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

const child0 = exec('ffmpeg -f video4linux2 -i /dev/video0 -vframes 1 test0.jpg',
  (error, stdout, stderr) => {
    console.log(`stdout: ${stdout}`);
    console.log(`stderr: ${stderr}`);
    if (error !== null) {
      console.log(`exec error: ${error}`);
    }
});
const child1 = exec('ffmpeg -f video4linux2 -i /dev/video1 -vframes 1 test1.jpg',
  (error, stdout, stderr) => {
    console.log(`stdout: ${stdout}`);
    console.log(`stderr: ${stderr}`);
    if (error !== null) {
      console.log(`exec error: ${error}`);
    }
});
const child2 = exec('ffmpeg -f video4linux2 -i /dev/video2 -vframes 1 test2.jpg',
  (error, stdout, stderr) => {
    console.log(`stdout: ${stdout}`);
    console.log(`stderr: ${stderr}`);
    if (error !== null) {
      console.log(`exec error: ${error}`);
    }
});