macOS has only 16K ports available that won't be released until socket TIME_WAIT is passed. The default timeout for TIME_WAIT is 15 seconds. Consider reducing in case of available port bottleneck.
You can check whether this is a problem with netstat:
$ sysctl net.inet.tcp.msl
net.inet.tcp.msl: 15000
$ sudo sysctl -w net.inet.tcp.msl=1000
net.inet.tcp.msl: 15000 -> 1000
| launchctl limit maxfiles | |
| sudo launchctl limit maxfiles 65536 200000 | |
| $ sysctl kern.maxfiles | |
| kern.maxfiles: 12288 | |
| $ sysctl kern.maxfilesperproc | |
| kern.maxfilesperproc: 10240 | |
| $ sudo sysctl -w kern.maxfiles=1048600 | |
| kern.maxfiles: 12288 -> 1048600 | |
| $ sudo sysctl -w kern.maxfilesperproc=1048576 | |
| kern.maxfilesperproc: 10240 -> 1048576 | |
| $ ulimit -S -n | |
| 256 | |
| $ ulimit -S -n 1048576 | |
| $ ulimit -S -n | |
| 1048576 | |
| # https://wilsonmar.github.io/maximum-limits/ |