I am trying to access a listening tcp socket on my macbook from any external client on the same wi-fi lan.

This works for specific ports, eg. 8000, but not other ports, eg. 8080, 8081, 8082

How can I open up or access the 8080 tcp port externally?

Working steps on port 8000

Server

$ nc -lv 8000

Client

$ nc -z 192.168.101.98 8000
Connection to 192.168.101.98 port 8000 [tcp/irdmi] succeeded!

Non-working steps on port 8080

Server

$ nc -lv 8080

Client

$ nc -z 192.168.101.98 8080
(The command just hangs)

Diagnostics

$ lsof -P -i TCP:8000
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
nc 75782 ... 3u IPv4 0x5be3e11e5a732339 0t0 TCP *:8000 (LISTEN)

$ lsof -P -i TCP:8080
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
nc 75952 ... 3u IPv4 0x5be3e11e581e2fb9 0t0 TCP *:8080 (LISTEN)

$ sudo pfctl -s all | grep Status
No ALTQ support in kernel
ALTQ related functions disabled
Status: Disabled Debug: Urgent

I am running macOS Mojave 10.14.1 (same behavior on 10.14 as well).

Update

I changed nothing, everything suddenly works. I am very curious what made the difference. Will close the question, if everything keeps working.