BASH command to save a node script that will listen on port 6677 for IP address from a SubText BBS

udp_firewall.js

cat <<'EOF' > /usr/local/bin/udp_firewall.js
const dgram = require('dgram');
const { exec } = require('child_process');

const PORT = 6677;

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

server.on('listening', () => {
  const address = server.address();
  console.log(`UDP server listening on ${address.address}:${address.port}`);
});

server.on('message', (msg, rinfo) => {
  const ipAddress = msg.toString().trim();
  console.log(`Received IP address: ${ipAddress}`);

  // Ban the IP address using iptables
  const commands = [
    `sudo iptables -A INPUT -s ${ipAddress} -j DROP`,
    `sudo iptables -A OUTPUT -d ${ipAddress} -j DROP`,
    `sudo iptables -A FORWARD -s ${ipAddress} -j DROP`,
    `sudo iptables -A FORWARD -d ${ipAddress} -j DROP`
  ];

  commands.forEach((command) => {
    exec(command, (error, stdout, stderr) => {
      if (error) {
        console.error(`Error executing command: ${command}`);
        console.error(`Error: ${error.message}`);
        return;
      }
      console.log(`Command executed: ${command}`);
    });
  });

  // Save the new iptables rules using netfilter-persistent
  exec('sudo netfilter-persistent save', (error, stdout, stderr) => {
    if (error) {
      console.error('Error saving iptables rules using netfilter-persistent');
      console.error(`Error: ${error.message}`);
      return;
    }
    console.log('New iptables rules saved using netfilter-persistent');
  });
});

server.on('error', (err) => {
  console.error(`UDP server error: ${err.message}`);
  server.close();
});

server.bind(PORT);
EOF