# WHATPORT(4005)

## NAME

port 4005 — SWANK (SLIME Lisp backend) — A Common Lisp SWANK server — a full remote REPL into a running Lisp image, usually with no authentication.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA registers 4005 as pxc-pin, but in practice this is the default port of SWANK, the backend that SLIME loads into a Common Lisp image so Emacs can drive it. A developer runs (swank:create-server) or starts a Lisp with SWANK loaded, then connects from Emacs with M-x slime-connect. Anything that can speak the SWANK protocol to that port can evaluate arbitrary Lisp inside the process, which is the whole point of the tool and also its entire risk profile.

## EXPOSURE

**Do not expose.** SWANK is remote code execution by design and ships with no authentication; bind it to 127.0.0.1 and reach it over an SSH tunnel.

## CHECK

```sh
nc -vz -w 3 TARGET 4005
```

## SEE ALSO

- docs — [SLIME manual — Setting up the Lisp image (default port 4005)](https://common-lisp.net/project/slime/doc/html/Setting-up-the-lisp-image.html) (common-lisp.net)
- source — [slime/slime](https://github.com/slime/slime) (github.com)
- iana — [IANA port registry — 4005 (pxc-pin)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=4005) (iana.org)

---

HTML: <https://whatport.net/4005/> · JSON: <https://whatport.net/4005.json> · full dataset: <https://whatport.net/ports.json>