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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.

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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:
ParameterTypeRequiredDescription
portLiteral[3000, 1337, 1338]YesPort 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 
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())