port-sniffer task

submissions/Vitamin/port-sniffer/helpers.js

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+const help = `
+    Usage: sniffer.js [--help] [--ports <number>-<number>] [--host <value>]
+
+    These are commands used in sniffer application: 
+
+        host       Host address, IP or URL.
+                   Examples: --host ukr.net,
+                             --host 172.217.3.110
+
+        ports      Ports range. Numbers must be more than 0 and less than 65535.
+                   Examples: --ports 30-562,
+                             --ports 1-65535.
+
+        help       Show all commands.
+`;
+
+const isDefined = value => value != null;
+
+module.exports = { help, isDefined };

submissions/Vitamin/port-sniffer/sniffer.js

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+const Net = require('net');
+const dns = require('dns').promises;
+const { help, isDefined } = require('./helpers');
+
+const [, , ...processArgs] = process.argv;
+const [minPortValue, maxPortValue] = [0, 65535];
+
+const ipFromHostname = async host => {
+  try {
+    const result = await dns.lookup(host);
+    return result.address;
+  } catch (err) {
+    throw Error('Invalid host');
+  }
+};
+
+const isPortInRange = port => port >= minPortValue && port <= maxPortValue;
+
+// eslint-disable-next-line consistent-return
+const getPortsRange = ports => {
+  const [firstPort, last] = ports.split('-');
+  const lastPort = isPortInRange(last) ? last : firstPort;
+  if (isPortInRange(firstPort)) {
+    return [firstPort, lastPort];
+  }
+  console.log('Invalid ports range');
+};
+
+const tryToConnect = (host, port) => {
+  const client = new Net.Socket();
+  client.setTimeout(300);
+  client.connect({ port, host });
+  return new Promise(resolve => {
+    client.on('connect', () => {
+      process.stdout.write('.');
+      client.destroy();
+      return resolve(port);
+    });
+    client.on('timeout', () => {
+      client.destroy();
+      return resolve(null);
+    });
+    client.on('error', () => {
+      client.destroy();
+      return resolve(null);
+    });
+  });
+};
+
+const getOpenedPorts = async ({ host, firstPort, lastPort }) => {
+  const promises = [];
+  // eslint-disable-next-line no-plusplus
+  for (let i = firstPort; i <= lastPort; i++) {
+    promises.push(tryToConnect(host, i));
+  }
+  const ports = await Promise.all(promises);
+  return ports.filter(isDefined);
+};
+
+const parseArguments = async args => {
+  if (args.includes('--help')) {
+    console.log(help);
+    process.exit(0);
+  } else if (
+    args.length < 4 ||
+    !args.includes('--ports') ||
+    !args.includes('--host')
+  ) {
+    console.log('Use --help to correct input');
+    process.exit(1);
+  }
+  const [firstPort, lastPort] = getPortsRange(args[1]);
+  const host = await ipFromHostname(args[3]);
+  return { host, firstPort, lastPort };
+};
+
+const getMessageToLog = openPorts => {
+  let result;
+  if (openPorts.length > 1) {
+    result = `\n${openPorts} ports are opened`;
+  } else if (openPorts.length === 1) {
+    result = `\n${openPorts} port is opened`;
+  } else {
+    result = '\nAll ports in range are closed';
+  }
+  return result;
+};
+
+const sniff = async args => {
+  const { host, firstPort, lastPort } = await parseArguments(args);
+  return getOpenedPorts({ host, firstPort, lastPort });
+};
+
+sniff(processArgs)
+  .then(getMessageToLog)
+  .then(console.log);