> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fermion.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Expose Ports from Sandbox for a Public HTTPS URL

> Expose a sandbox port publicly over HTTPS and access live web services running inside the container using the Python SDK.

The `expose_port()` method provides a **public HTTPS URL** that maps directly to a specific port running inside your sandbox container.\
Fermion automatically supports ports **3000**, **1337**, and **1338**, allowing you to host web servers, APIs, or other networked services securely and access them from anywhere.

When you start a server inside your sandbox (for example, using `python -m http.server` or `node server.js`), you can call `expose_port(port)` to instantly retrieve a URL in the format:`https://{subdomain}-{port}.run-code.com`

This allows you to preview, test, and share live web apps or APIs running within your sandbox.

***

### `async expose_port(port: Literal[3000, 1337, 1338]) -> str`

**Description:**\
Returns the public HTTPS URL for a specific port inside the sandbox.\
Currently, Fermion supports public exposure for ports **3000**, **1337**, and **1338**.

***

**Parameters:**

| Parameter | Type                        | Required | Description                                            |
| --------- | --------------------------- | -------- | ------------------------------------------------------ |
| `port`    | `Literal[3000, 1337, 1338]` | Yes      | Port number (must be one of `3000`, `1337`, or `1338`) |

***

**Returns:**\
`str` : Public HTTPS URL in the format `https://{subdomain}-{port}.run-code.com`.

***

**Example - Start and expose a Node.js server**

```python theme={null}
import asyncio
import time
from fermion_sandbox import Sandbox
import requests

async def main():
    sandbox = Sandbox(api_key="your-api-key")
    await sandbox.create(should_backup_filesystem=False)

    # Write a simple Node.js server
    await sandbox.write_file(
        path="/home/damner/server.js",
        content="""
const http = require('http');
http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello from Fermion!');
}).listen(3000, () => {
  console.log('Server running on port 3000');
});
"""
    )

    # Run the server in the background with streaming output
    server_task = asyncio.create_task(
        sandbox.run_streaming_command(
            cmd="node",
            args=["/home/damner/server.js"],
            on_stdout=lambda data: print("[stdout]", data.strip())
        )
    )

    # Wait briefly for the server to start
    await asyncio.sleep(2)

    # Retrieve the public HTTPS URL for the exposed port
    url = await sandbox.expose_port(3000)
    print("Access your server at:", url)
    # Example output: https://abc123xyz-3000.run-code.com

    # Test the server.
    response = requests.get(url)
    print(response.text)  # Output: Hello from Fermion!

asyncio.run(main())
```