# Port configuration
### How routing works
Every web services come with default domain, optionally you an set a custom domain. All requests pass through our load balancer as follows:
Let's say your app starts and listen for requests on port `4000`
Our load balancer is configured the way that every request coming to your app on port `443` or `80` are proxied to port `4000` of your app
### Examples
#### Flask example:
1. Let's say your app is configured to start on port `4000`
**app.py**
```python
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello():
return "Hello, World!"
if __name__ == "__main__":
app.run(host="0.0.0.0", port=4000)
```
2. Set the port to `4000`
3. Follow the next steps by clicking continue
4. Now when the app is built and deployed successfully you can connect to your app by:
1. Public connection domain (user for access from the internet)
2. Private connection domain (use for internal connections between your services)
