Recently I wasted several hours wrangling my dev environment only to find out that the browser frontend was talking to the wrong version of the backend. This got me thinking--why on earth are we still using simple numbers to describe which process to connect to? Why not use names instead? I thought of all the times a program wouldn't start because of port conflicts. The more I thought about it, the crazier it seemed.
Modern operating systems already offer no-conflict ports: if you make your TCP server listen on port 0, the OS assigns you a random available port. But that only solves half the problem.
I built the other half: PortZero. It's a GPLv3 program that watches for processes (and docker containers!) with a special PZ_TUNNEL environment variable:
PZ_TUNNEL=myapp-{branch}.portzero.local:80 npm run dev
1. Create a virtual NIC (if it hasn't already)
2. Create a new virtual IP address
3. Create a DNS record that substitutes things like {branch} based on the working directory of the process, and points at that virtual IP address
4. Start listening on that virtual IP address on the port of your choice (e.g. port 80 for http, port 443 for https, port 5432 for postgresql)
5. Forward any TCP connections to that virtual IP address / virtual port to the random, OS-assigned port that your process or container is actually listening on
The result is you don't have to think about ports anymore, you just have to think about subdomains. You can have multiple services available on port 80 without conflicts, as long as they have different portzero.local subdomains.
It does some other cool stuff like:
- Enable HTTPS on local HTTP services by creating a local CA and registering it on your machine
- Enable cloud tunnels so you can access your apps on other devices (paid feature)
Links:
I have never faced this problem even though I hard-code the port. It's because I run the server program through VS Code's debugger. If there's already a session, it would warn me.
Not super popular, but: https://en.wikipedia.org/wiki/SRV_record
But at a larger level this tool just makes everything work so smoothly. If you have two services with the same name, it pops up a notification in the tray. If you start a new process with a different name, you don't have to configure SRV; the DNS just becomes available automatically. HTTPS is auto configured. That sort of thing.
I think somebody could one day make something like this that was based on SRV, but it would still need all those niceties to make it work well for developers.
- old / zombie server processes
- sockets that weren't properly cleaned up
- TIME_WAITs
my solution wasn't anything as clever as OPs though. Basically, I ended up conceiving of 127/8 as a rotating ring. Where you can pass offsets and easily end up on an unused bind tup every time. 127/8 gives you a huge number of IPs to play with. You just make address handling part of your test launcher and it sets a new IP each time.
The issue is it doesn't really work for IPv6 (v6 localhost is only one address!) Though global-scope v6 interface blocks and manually assigned link-local scope, you could accomplish much the same thing.
[1] https://chaosnet.net/protocol#application_layer [2] https://datatracker.ietf.org/doc/html/rfc1078