# Public URL
Get the public URL of the sandbox and connect to the service running in the sandbox.
Each sandbox is accessible via a public URL, which allows you to expose and connect to the services running within it. This page describes how to obtain the URL, connect to a server within the sandbox, and customize the `Host` header received by the service.
To control outbound Internet access from the sandbox, see [Network Access](/docs/agent-sandbox/network/internet-access.md). To require authentication on public URLs, see [Restrict Public Access](/docs/agent-sandbox/network/restrict-public-access.md).
## Sandbox public URL
Each sandbox has a public URL that can be used to access services running within the sandbox.
```python
from ucloud_sandbox import Sandbox
sandbox = Sandbox.create()
# Always need to pass in the port number when getting the host
host = sandbox.get_host(3000)
print(f'https://{host}')
```
The above code will print something similar to the following:
```bash
https://3000-.cn-wlcb.sandbox.ucloudai.com
```
The first left-most part of host is the port number we passed to the method.
## Connect to a server running within the sandbox
You can start the server inside the sandbox and connect to it using the method above.
In this example, we will start a simple HTTP server that listens on port 3000 and returns the contents of the directory where the server was started.
```python
import requests
from ucloud_sandbox import Sandbox
sandbox = Sandbox.create()
# Start a simple HTTP server in the sandbox
process = sandbox.commands.run("python -m http.server 3000", background=True)
host = sandbox.get_host(3000)
url = f"https://{host}"
print('Server started at:', url)
# Get data from the server in the sandbox
response = requests.get(url)
data = response.text
print('Response from server inside sandbox:', data)
# Kill the server process in the sandbox
process.kill()
```
The output will look like this:
```bash
Server started at: https://3000-.cn-wlcb.sandbox.ucloudai.com
Response from server inside sandbox:
Directory listing for /
Directory listing for /
```
## Mask request Host header
You can use the `mask_request_host` option to customize the `Host` header sent to services running inside the sandbox. This is useful when your application requires a specific host format.
```python
from ucloud_sandbox import Sandbox
# Create a sandbox with custom host mask
sandbox = Sandbox.create(
network={
"mask_request_host": "localhost:${PORT}"
}
)
# ${PORT} variable will be replaced with the actual port number
# The Host header of requests sent to the sandbox will be set to, for example: localhost:8080
```
The `${PORT}` variable in the mask is automatically replaced with the actual port number of the requested service.