filewatcher1_node-introduction.js

//filewatcher.js

const net = require('net'),
   fs = require('fs'),
   filename = process.argv[2],
      
server = net.createServer((connection)=>{
 console.log('Subscriber connected');
 connection.write(`watching ${filename} for changes`);
  
let watcher = fs.watch(filename,(err,data)=>{
  connection.write(`${filename} has changed`);
 });
  
connection.on('close',()=>{
  console.log('Subscriber disconnected');
  watcher.close();
 });
  
});
server.listen(3000,()=>console.log('listening for subscribers'));