How to Access FastAPI Backend from a Different Machine/IP on the Same Local Network

To access a FastAPI backend from a different machine on the same local network, it's essential to ensure the following:

1. Host Flag Configuration:

Set the host flag to 0.0.0.0 when running the FastAPI server. This allows the server to listen on all available IP addresses on the local machine.

2. Firewall Adjustments:

Ensure that the firewall is configured to allow inbound connections on the specified port for the FastAPI app. This may require creating an inbound firewall rule for Python.

3. CORS Settings:

Enable and configure CORS (Cross-Origin Resource Sharing) in your FastAPI app. This allows cross-domain requests between the frontend and backend, which may occur when different IP addresses and port numbers are used.

4. HTTP Requests in JavaScript:

In the frontend JavaScript, use the correct origin/URL when making fetch requests to the FastAPI backend. The origin should match the domain name typed into the browser's address bar.

Example CORS Settings for FastAPI:

origins = ['http://localhost:3000', 'http://192.168.x.x:3000']

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=['*'],
    allow_headers=['*'],
)

Proper Origin Usage in JavaScript:

fetch('http://192.168.x.x:3000/people', {...

By following these steps, you can successfully access your FastAPI backend from a different machine on the same local network.