# Identifying ports already in use

```
$ lsof -i -n -P | grep TCP | grep 4000
beam.smp  28569 mnishiguchi   49u  IPv4 0x4d3d8b73de14af89      0t0  TCP *:4000 (LISTEN)

$ kill -9 28569
```

## Resources

- [Identifying ports in use on Mac and Windows Operating Systems](https://help.extensis.com/hc/en-us/articles/360004935154-Identifying-ports-in-use-on-Mac-and-Windows-Operating-Systems)