Comment by embedding-shape

4 hours ago

I'm not sure how I'd do acceptance/E2E testing without the magic of port 0. As long as you have a way of capturing what port it ended up using (which most languages are able to out of the box more or less), parallelizing testing workloads becomes such a breeze without having to manage ports and all that jazz, just fire everything up with N parallism and let the OS figure out what the free ports are, pass the references down and stuff just works. Thanks Linux :)

3 comments

embedding-shape

wolrah 30 minutes ago

> I'm not sure how I'd do acceptance/E2E testing without the magic of port 0.

Same as anything else, an explicit flag to achieve the same "just give me a port" functionality as this "magic number" does without resulting in the documented unpredictable behavior around a technically legitimate port number.

As the article points out, most if not all of the services exposed on port 0 seem to be accidental and likely resulted from people assuming this magic behavior applies everywhere instead of just to one specific API.

embedding-shape 5 minutes ago

> Same as anything else
Yeah, obviously I'm a programmer so I'm well aware it's technically possible, it was a bit of an exaggeration to explain how much value I feel I get from it.
> most if not all of the services exposed on port 0 seem to be accidental
No program actually end up "exposed on port 0", if it's not supported it won't be able to create a listener on that port, AFAIK. Most yeah, all no. P2P software commonly leverage port 0, and other "discover<>connect" types of software. But I'd agree that it's most likely accidental if outside of those niches.

Joker_vD 1 hour ago

And then there is OpenSSH...

    joker@joker:~$ ssh localhost -D 127.0.0.1:0
    Bad dynamic forwarding specification '127.0.0.1:0'
    joker@joker:~$ ssh localhost -D 127.0.0.1:9999
    ssh: connect to host localhost port 22: Connection refused
    joker@joker:~$ ssh localhost -L 127.0.0.1:0:localhost:8080
    Bad local forwarding specification '127.0.0.1:0:localhost:8080'
    joker@joker:~$ ssh localhost -L 127.0.0.1:9999:localhost:8080
    ssh: connect to host localhost port 22: Connection refused

Oh well.