From 6958ec5d61f3635c333c823793932cc47a16d725 Mon Sep 17 00:00:00 2001
From: Dmytro Klymenko <dmytro.klymenko@protonmail.com>
Date: Mon, 6 Sep 2021 08:51:45 +0300
Subject: [PATCH 1/2] #4819 rewrite the check port script with built-in
 isPackagerRunning function and rename the script

---
 config/checkMetroBundlerPort.js | 11 ++++++++++
 config/checkPort.js             | 39 ---------------------------------
 package.json                    | 10 ++++-----
 3 files changed, 16 insertions(+), 44 deletions(-)
 create mode 100644 config/checkMetroBundlerPort.js
 delete mode 100644 config/checkPort.js

diff --git a/config/checkMetroBundlerPort.js b/config/checkMetroBundlerPort.js
new file mode 100644
index 000000000000..a7ad0bc7621d
--- /dev/null
+++ b/config/checkMetroBundlerPort.js
@@ -0,0 +1,11 @@
+const {isPackagerRunning} = require('@react-native-community/cli-tools');
+
+isPackagerRunning().then((result) => {
+    if (result === 'unrecognized') {
+        console.error(
+            'The port 8081 is currently in use.',
+            'You can run `lsof -i :8081` to see which program is using it.\n',
+        );
+        process.exit(1);
+    }
+});
diff --git a/config/checkPort.js b/config/checkPort.js
deleted file mode 100644
index 24e3efef3679..000000000000
--- a/config/checkPort.js
+++ /dev/null
@@ -1,39 +0,0 @@
-const net = require('net');
-
-function checkPort(port, host) {
-    return new Promise((resolve, reject) => {
-        const server = net.createServer();
-        server.once('error', (err) => {
-            if (err.code !== 'EADDRINUSE') {
-                return reject(err);
-            }
-
-            reject(err);
-        });
-        server.once('listening', () => {
-            server.once('close', () => resolve(false));
-            server.close();
-        });
-        server.listen(port, host);
-    });
-}
-
-const inputPort = Number(process.argv.slice(2)[0]);
-if (Number.isNaN(inputPort) || inputPort < 0 || inputPort > 65535) {
-    console.error('This command requires an argument that must be a number [0-65535]\n');
-    process.exit(1);
-}
-
-Promise.all([
-    checkPort(inputPort, 'localhost'),
-    checkPort(inputPort, '127.0.0.1'),
-    checkPort(inputPort, '0.0.0.0'),
-])
-    .then(() => process.exit(0))
-    .catch(() => {
-        console.error(
-            `The port ${inputPort} is currently in use.`,
-            `You can run \`lsof -i :${inputPort}\` to see which program is using it.\n`,
-        );
-        process.exit(1);
-    });
diff --git a/package.json b/package.json
index 80c1cce06c33..4b053901eee4 100644
--- a/package.json
+++ b/package.json
@@ -7,10 +7,10 @@
   "license": "MIT",
   "private": true,
   "scripts": {
-    "android": "npm run check-port -- 8081 && react-native run-android",
-    "ios": "npm run check-port -- 8081 && react-native run-ios",
-    "ipad": "npm run check-port -- 8081 && react-native run-ios --simulator=\"iPad Pro (12.9-inch) (4th generation)\"",
-    "ipad-sm": "npm run check-port -- 8081 && react-native run-ios --simulator=\"iPad Pro (9.7-inch)\"",
+    "android": "npm run check-metro-bundler-port && react-native run-android",
+    "ios": "npm run check-metro-bundler-port && react-native run-ios",
+    "ipad": "npm run check-metro-bundler-port && react-native run-ios --simulator=\"iPad Pro (12.9-inch) (4th generation)\"",
+    "ipad-sm": "npm run check-metro-bundler-port && react-native run-ios --simulator=\"iPad Pro (9.7-inch)\"",
     "desktop": "node desktop/start.js",
     "start": "react-native start",
     "web": "node web/proxy.js & webpack-dev-server --open --config config/webpack/webpack.dev.js",
@@ -30,7 +30,7 @@
     "gh-actions-build": "./.github/scripts/buildActions.sh",
     "gh-actions-validate": "./.github/scripts/validateActionsAndWorkflows.sh",
     "analyze-packages": "ANALYZE_BUNDLE=true webpack --config config/webpack/webpack.prod.js",
-    "check-port": "node config/checkPort.js"
+    "check-metro-bundler-port": "node config/checkMetroBundlerPort.js"
   },
   "dependencies": {
     "@formatjs/intl-getcanonicallocales": "^1.5.8",

From da90f41f56bb44d8d73b1478da3c5659eaf90acc Mon Sep 17 00:00:00 2001
From: Dmytro Klymenko <dmytro.klymenko@protonmail.com>
Date: Thu, 9 Sep 2021 19:22:31 +0300
Subject: [PATCH 2/2] #4819 add comment with isPackagerRunning function
 description

---
 config/checkMetroBundlerPort.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/config/checkMetroBundlerPort.js b/config/checkMetroBundlerPort.js
index a7ad0bc7621d..4c8d017fc1e0 100644
--- a/config/checkMetroBundlerPort.js
+++ b/config/checkMetroBundlerPort.js
@@ -1,5 +1,12 @@
 const {isPackagerRunning} = require('@react-native-community/cli-tools');
 
+/**
+ * Function isPackagerRunning indicates whether or not the packager is running. It returns a promise that
+ * returns one of these possible values:
+ *   - `running`: the packager is running
+ *   - `not_running`: the packager nor any process is running on the expected port.
+ *   - `unrecognized`: one other process is running on the port we expect the packager to be running.
+ */
 isPackagerRunning().then((result) => {
     if (result === 'unrecognized') {
         console.error(