Added checkIfPortIsUse

Author: luca-vogels

package.json

@@ -1,6 +1,6 @@
 {
   "name": "lup-system",
-  "version": "1.4.0",
+  "version": "1.5.0",
   "description": "NodeJS library to retrieve system information and utilization.",
   "main": "./lib/index",
   "types": "./lib/index.d.ts",

src/__tests__/Net.test.ts

@@ -1,10 +1,32 @@
-import { getNetworkInterfaces, stopNetworkUtilizationComputation } from '../net';
+import { checkIfPortIsInUse, getNetworkInterfaces, stopNetworkUtilizationComputation } from '../net';
+import net from 'net';
 
 test('getNetworkInterfaces', async () => {
   const nics = await getNetworkInterfaces();
-  console.log(nics); // TODO REMOVE
+  //console.log(nics); // TODO REMOVE
+  expect(nics).toBeDefined();
+  expect(nics.length).toBeGreaterThan(0);
 }, 10000);
 
+test('checkIfPortIsInUse(12345)', async () => {
+  const port = 12345;
+
+  // port should be free
+  const isInUse1 = await checkIfPortIsInUse(port);
+  expect(isInUse1).toBe(false);
+
+  // start a server
+  const server = net.createServer();
+  server.unref();
+  await new Promise<void>((resolve) => server.listen(port, '0.0.0.0', resolve));
+
+  // port should now be in use
+  const isInUse2 = await checkIfPortIsInUse(port);
+  expect(isInUse2).toBe(true);
+
+  server.close();
+});
+
 afterAll(() => {
   stopNetworkUtilizationComputation();
 });

src/net.ts

@@ -1,5 +1,6 @@
 import { execCommand } from './utils';
 import fs from 'fs/promises';
+import net from 'net';
 import os from 'os';
 
 export type NICUtilization = {
@@ -167,6 +168,33 @@ export function stopNetworkUtilizationComputation() {
   NET_COMPUTE_RUNNING = false;
 }
 
+
+/**
+ * Checks if a process is listening on a given port.
+ * @param port Port number to check.
+ * @param bindAddress Address of the interface to bind to (default '0.0.0.0' which binds to all interfaces).
+ * @returns Promise that resolves to true if the port is in use, false otherwise.
+ */
+export async function checkIfPortIsInUse(port: number, bindAddress: string = '0.0.0.0'): Promise<boolean> {
+  const server = net.createServer();
+  return new Promise((resolve) => {
+    server.unref();
+    server.once('error', (err) => {
+      server.close();
+      if((err as any).code === 'EADDRINUSE') {
+        resolve(true);
+      } else {
+        resolve(false);
+      }
+    });
+    server.listen(port, bindAddress, () => {
+      server.close();
+      resolve(false);
+    });
+  });
+}
+
+
 /**
  * Returns information about the network interfaces on the system.
  *