const net = require('net');
const fs = require('fs');

const PORT = 9100;
const FILE_PATH = 'data.txt';

const server = net.createServer((socket) => {
  console.log('Client connected');

  socket.on('data', (data) => {
    fs.appendFile(FILE_PATH, data, (err) => {
      if (err) {
        console.error(err);
      } else {
        console.log('Data written to file');
      }
    });
  });

  socket.on('end', () => {
    console.log('Client disconnected');
  });

  socket.on('error', (err) => {
    console.error(err);
  });
});

server.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});