Why does uvicorn's --host parameter change depending on whether you are on a local VM, a production server, or inside Docker? A look into socket binding and network isolation.
There is a line in almost every Python web tutorial that nobody explains:
uvicorn main:app --host 0.0.0.0 --port 8000
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I copied it for weeks without thinking about it. Then I deployed the same application three times — to a local VM, to a production server, and into a container — and the correct value was different every time.
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