test: flaky parallel/test-net-connect-local-error on macOS & freeBSD

[refack]

• Version: master
• Platform: macOS,freeBSD
• Subsystem: test

https://ci.nodejs.org/job/node-test-commit-freebsd/8933/nodes=freebsd11-x64/tapResults/
https://ci.nodejs.org/job/node-test-commit-osx/9696/nodes=osx1010/tapResults/

738	parallel/test-net-connect-local-error	
duration_ms	
0.162
severity	
fail
stack	
Mismatched onError function calls. Expected 1, actual 0.
 at Object.<anonymous> (/Users/iojs/build/workspace/node-test-commit-osx/nodes/osx1010/test/parallel/test-net-connect-local-error.js:15:27)
 at Module._compile (module.js:569:30)
 at Object.Module._extensions..js (module.js:580:10)
 at Module.load (module.js:503:32)
 at tryModuleLoad (module.js:466:12)
 at Function.Module._load (module.js:458:3)
 at Function.Module.runMain (module.js:605:10)
 at startup (bootstrap_node.js:144:16)
 at bootstrap_node.js:537:3

[sebastianplesciuc]

Can I take this one?

[refack]

@sebastianplesciuc you like these ones 😉 . dibs is yours.
P.S. I've been told that the use of common.PORT is fragile in macOS / freeBSD.
There's a general goal to use 0 as port (if possible) and then figure out which port the OS assigned.

[refack]

Ref: #12376

[sebastianplesciuc]

I think that's the case here as well.

I think there are two issues with this, one is that server.close() might be called before the client's callback which is the error on line 15 I believe.

Another issue might arise with port + 1. We have no guarantee that this is an empty port when this runs. A way of fixing this might be creating another server with port 0 and assigning it's port to the client socket in it's close callback. Thoughts? Is it guaranteed to be in use while the callback is running from net.Server close event?

[refack]

1. The close is definitely in a bad place
2. When net.Server.close call the cb the server will not answer anymore, so it's a good time to try to connect to it (to get an error)
   Another option is to loop port + 1...5, if that's simpler.

Worse case we can move it to /sequential/ where it will run alone.

[refack]

@sebastianplesciuc You might appreciate this. I've been looking at this issue's brother #12951.
These tests are run in parallel first this one, then the other.
In the other one there's a server that's supposed to receive 6 connections, instead it received 7.
I wonder where that 7th request comes from 🤣

[sebastianplesciuc]

@refack I'm not sure I get it :) You're suggesting that the connection in that test comes from this one? How does that work?

[sebastianplesciuc]

@refack OOOOH! I think I get it now. So when that test fails, this test fails because it connects from this test to the server from that test. So fixing this test would fix that one?