Detect if a module has been run directly from Node.js or imported, read more: https://nodejs.org/api/modules.html#modules_accessing_the_main_module

server.js

const dgram = require('dgram');

let server = dgram.createSocket('udp4');

function bind(socket, port = 8088, address = '0.0.0.0', callback = () => {}) {
  socket.bind(port, address, callback);
}

// Bind server only if module was run directly, eg. node server.js
 if (require.main === module) {
  bind(server, process.env.PORT, process.env.HOST);
 }

module.exports = {
  server,
  bind
}