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RobL
RobL

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Petty Annoyances #4929

#webdev #rails #ruby #puma

Not every Rails app is run on port 3000, if you're fortunate enough to be managing more than one application over the course of your work you may well have a server boot script.

#!/bin/bash rails server -b 0.0.0.0 --port=7000 -u puma
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Running apps on 3000, 4000, 5000, 6000, 7000, and beyond. That's plenty of apps. And then one day you get...

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Address already in use - bind(2) for "0.0.0.0" port 7000 (Errno::EADDRINUSE)
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You'd be forgiven for thinking that you're already running the app in another tab, that's happened before. Nope...

Well, we can netstat and take a look. This is a trimmed down result.

rl@Robs-MacBook-Pro-2 someapp % netstat -ant | grep LISTEN tcp6 0 0 *.5000 *.* LISTEN tcp4 0 0 *.5000 *.* LISTEN tcp6 0 0 *.7000 *.* LISTEN tcp4 0 0 *.7000 *.* LISTEN tcp4 0 0 *.443 *.* LISTEN tcp4 0 0 *.80 *.*
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Yep it's running as well as something else on port 5000. 443 and 80 (that's puma-dev). So ports 5000, 7000 are running even though I know the apps that are assigned those ports aren't.

Well, I won't keep the suspense. It's Apple AirPlay. If you go to System Preferences > Sharing, you'll it running.

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Untick that.

rl@Robs-MacBook-Pro-2 someapp % netstat -ant | grep LISTEN tcp4 0 0 *.443 *.* LISTEN tcp4 0 0 *.80 *.*
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And now our app boots unhindered.

rl@Robs-MacBook-Pro-2 someapp % ./bin/server => Booting Puma => Rails 6.1.7 application starting in development => Run `bin/rails server --help` for more startup options [DEPRECATED] ActiveSupportBackports should no longer be needed. Please remove! Puma starting in single mode... * Puma version: 5.4.0 (ruby 2.7.6-p219) ("Super Flight") * Min threads: 5 * Max threads: 5 * Environment: development * PID: 18359 * Listening on http://0.0.0.0:7000 Use Ctrl-C to stop
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