[Bug] Multiple ports for multiple instance

[xihale]

Current State:

When attempting to run two separate instances of Zine, each associated with a different project, both instances default to using port 1990. This results in a port conflict, preventing the second Zine instance from starting successfully or being accessible.

Expected Behavior:

Each Zine instance should ideally operate on a unique and available port to allow for simultaneous, independent operation of multiple projects.

[Spiffyk]

Just for the sake of completeness: you can already do this manually by using the --port [number] option.

(Also, just a nitpick: the default port is 1990, not 1900)

[xihale]

Just for the sake of completeness: you can already do this manually by using the --port [number] option.

(Also, just a nitpick: the default port is 1990, not 1900)

Thank you for the reminder and correction.

When the default port is in use, it would be more user-friendly to have a simpler solution, such as automatically assigning a random port and providing clear feedback about any port conflicts and the new port.
Could we have this?

[Spiffyk]

To be clear, I actually have no say in this, it's not my project.

But my personal opinion is that having such automagical error fixing is more trouble than it's worth. Say e.g. I have an instance of Zine running already, but I forget about it, run another instance somewhere else and refresh the already-open webpage in my browser. Confusion ensues: why is it showing the previous website and not the new one??

I'm much more in favour of just showing an error when the port is already taken and telling me how to fix it manually.

(Now that I'm messing around with it, I have found an actual bug: Zine happily runs on the same port that another Zine is already running on! Seems like an incorrect use of REUSEPORT. I'm filing that.)

[Spiffyk]

The above bug is caused by Zine setting .reuse_address = true in the std.net.Address.listen call, which would be valid if .reuse_address meant the same as the SO_REUSEADDR socket option, but it incorrectly conflates it with SO_REUSEPORT, which (on Linux) means something different.

I think this should be fixed in std itself, not Zine. See ziglang/zig#24838 for more.

[xihale]

Thanks for your detecting, it is a great uncovery.