Question: Recently I tried to use Strapi.

I want run two Strapi apps in single server.
So I tried to change default port number - 1337 to other number (For example 1331)
In ./config/server.js file.

But when I tried to run Strapi, it failed.
In Terminal below is last message, and I can not access admin page - http://localhost:1331/admin

< Opening the admin panel... >

How can I change port number of Strapi?

Answer: 
You can easily change your **.env** file located in the root project directory adding this line:

```
PORT=8082
```

Then save the file, **and run this command in order to refresh up all the things:**

```
npm run build
```

now you can start your server by running:

```
npm run develop
```
You will find option to change the port in `config/server.js`

Please refer official docs link below fore more information.

<https://strapi.io/documentation/v3.x/concepts/configurations.html#server>