Fix/detect windows excluded ports

lib/portscanner.js

@@ -129,7 +129,28 @@ function checkPortStatus (port) {
   // Return after the socket has closed
   socket.on('close', function (exception) {
     if (exception && !connectionRefused) { error = error || exception } else { error = null }
-    callback(error, status)
+
+    // For windows localhost, we should check if the port is in excluded range by actually binding to it
+    if ((host === '127.0.0.1' || host === 'localhost') && process.platform === 'win32' && status === 'closed') {
+      var server = net.createServer()
+      server.on('error', function (e) {
+        if (e.code === 'EACCES') {
+          status = 'reserved'
+          error = null
+        }
+        server.close()
+      })
+      // on close, we should call the callback
+      server.on('close', function () {
+        callback(error, status)
+      })
+      server.listen(port, host, function () {
+        server.close()
+      })
+
+    } else {
+      callback(error, status)
+    }
   })
 
   socket.connect(port, host)
@@ -138,7 +159,7 @@ function checkPortStatus (port) {
  * Callback for {@link checkPortStatus}
  * @callback checkPortCallback
  * @param {Error|null} error - Any error that occurred while port scanning, or null.
- * @param {String} status - Status: 'open' if the port is in use, 'closed' if the port is available.
+ * @param {String} status - Status: 'open' if the port is in use, 'closed' if the port is available, or 'reserved' if the port is reserved (Windows only).
  */
 
 /**

test.js

@@ -1,4 +1,5 @@
 import net from 'net'
+import { execSync } from 'child_process'
 import test from 'ava'
 import portScanner from '.'
 
@@ -9,6 +10,7 @@ findPortNotInUse()
 promise()
 reverseOrder()
 portsAsStrings()
+findExcludedPorts()
 
 function initialize () {
   test.before.cb('Set #1 test server', t => {
@@ -487,3 +489,37 @@ function portsAsStrings () {
     })
   })
 }
+
+function findExcludedPorts () {
+  if (process.platform !== 'win32') return
+  const output = execSync(
+    'netsh interface ipv4 show excludedportrange protocol=tcp'
+  ).toString()
+  const ports = output
+    .split('\n')
+    .filter((line) => line.match(/^ +[0-9]+ +[0-9]+/))
+    .map((line) => line.match(/ +([0-9]+) +([0-9]+)/).slice(1, 3))
+  console.log(`ports:`, ports)
+  const portsToCheck = []
+  for (const [startPort, endPort] of ports) {
+    for (
+      let i = Number(startPort);
+      i <= Math.min(Number(startPort) + 2, endPort);
+      i++
+    ) {
+      portsToCheck.push(i)
+    }
+  }
+  if (!portsToCheck.length) return
+  console.log(`portsToCheck:`, portsToCheck)
+  test.cb('Test reserved ports on Windows', (t) => {
+    t.plan(portsToCheck.length)
+    for (const port of portsToCheck) {
+      console.log(`testing:`, port)
+      portScanner.checkPortStatus(port, function (error, status) {
+        console.log(port, { error, status })
+        t.is(status, 'reserved')
+      })
+    }
+  })
+}