Complete port-sniffer homework

submissions/OperKH/port-sniffer/sniffer.js

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+const net = require('net');
+
+function getParamsFromArguments () {
+  if (process.argv.includes('--help')) {
+    showHelp();
+    process.exit(0);
+  }
+  if (!process.argv.includes('--host')) {
+    process.stdout.write('--host is required');
+    process.exit(1);
+  }
+  return process.argv
+    .slice(2)
+    .join(' ')
+    .split(/\s?--/)
+    .reduce(function (acc, str) {
+      if (!str) return acc;
+      const [key, value] = str.split(' ');
+      switch (key) {
+        case 'help':
+          break;
+        case 'host':
+          if (!value) {
+            process.stdout.write('Host value must be provided, e.g. "--host 8.8.8.8"');
+            process.exit(1);
+          }
+          acc[key] = value;
+          break;
+        case 'ports':
+          if (!value) {
+            process.stdout.write('Ports value must be provided, e.g. "--ports 300-1024"');
+            process.exit(1);
+          }
+          if (!value.includes('-')) {
+            process.stdout.write('Ports format invalid, must be e.g. "--ports 300-1024"');
+            process.exit(1);
+          } else {
+            const [startPort, endPort] = value.split('-').map(port => parseInt(port, 10));
+            if (isNaN(startPort) || startPort < 0) {
+              process.stdout.write('Start port format invalid');
+              process.exit(1);
+            }
+            if (isNaN(endPort) || endPort < 0) {
+              process.stdout.write('End port format invalid');
+              process.exit(1);
+            }
+            if (endPort > 65535) {
+              process.stdout.write('End port must be between 0-65535');
+              process.exit(1);
+            }
+            if (startPort > endPort) {
+              process.stdout.write('End port must be bigger then start port');
+              process.exit(1);
+            }
+            acc.startPort = startPort;
+            acc.endPort = endPort;
+          }
+          break;
+        default:
+          acc[key] = value;
+      }
+      return acc;
+    }, {});
+}
+
+function showHelp () {
+  console.log(`NAME
+    TCP sniffer - scans open ports on specific host.
+
+OPTIONS
+    --help
+        Output a usage message and exit.
+
+    --host
+        Set a host for scan.
+        E.g. "--host 127.0.0.1".
+
+    --ports
+        Set ports to scan.
+        E.g. "--ports 300-1024".
+        Default values: 0-65535.
+
+EXAMPLES
+    node sniffer.js --host localhost
+    node sniffer.js --host localhost --ports 300-1024
+`);
+}
+
+function sniffConnectionAvailabilityAsync (port, host) {
+  return new Promise(function (resolve, reject) {
+    const socket = new net.Socket();
+    socket.setTimeout(300);
+
+    socket.on('connect', function () {
+      socket.destroy();
+      resolve();
+    });
+    socket.on('timeout', function () {
+      socket.destroy();
+      reject(new Error('timeout'));
+    });
+    socket.on('error', function (err) {
+      socket.destroy();
+      reject(err);
+    });
+
+    socket.connect(port, host);
+  });
+}
+
+async function scanAsync (host, port, portLimit, availablePorts = []) {
+  if (port > portLimit) {
+    return availablePorts;
+  }
+  try {
+    await sniffConnectionAvailabilityAsync(port, host);
+    process.stdout.write('.');
+    availablePorts.push(port);
+  } catch (e) {}
+  return scanAsync(host, port + 1, portLimit, availablePorts);
+}
+
+(async function () {
+  const { host, startPort = 0, endPort = 65535 } = getParamsFromArguments();
+  const openedPorts = await scanAsync(host, startPort, endPort);
+  const result = openedPorts.length ? `\n${openedPorts.join(',')} ports are opened` : `\nNo open ports on host: ${host}`;
+  process.stdout.write(result);
+  process.exit(0);
+})();