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Date: Wed, 06 May 2026 00:54:05 +0000
From: marvology@riseup.net
To: submit@bugs.debian.org
Subject: =?UTF-8?Q?epmd=2Esocket_fails_to_bind_to_127=2E0=2E0=2E1=3A4369_?=
 =?UTF-8?Q?with_=E2=80=9CAddress_already_in_use=E2=80=9D_even_when_nothing?=
 =?UTF-8?Q?_is_listening?=
Message-ID: <284ef9df0bf17daa164f6cf68220de14@riseup.net>
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Package: erlang-base
Version: 1:27.3.4.1+dfsg-1+deb13u1

Sure — here’s a concise bug report draft you can send to the Debian
maintainer.

I'm reporting an issue with the Debian epmd systemd socket/service
setup.

On my system, epmd initially appears to be listening on all interfaces:


ss -tulpn | grep epmd
tcp   LISTEN 0 4096 *:4369 *:*
users:(("epmd",pid=2368130,fd=3),("systemd",pid=1,fd=199))


I tried to restrict epmd to localhost by creating a systemd socket
override:


[Socket]
ListenStream=127.0.0.1:4369


After that, I ran:


systemctl daemon-reload
systemctl restart epmd.socket epmd.service


At that point, `pmd.socket failed to start with:


epmd.socket: Failed to create listening socket (127.0.0.1:4369): Address
already in use


This was surprising because no process appeared to be holding port 4369
at that point.

I checked with `ss`, and nothing was listening on 4369.
However, after removing the socket override entirely, running:


systemctl daemon-reload
systemctl restart epmd.socket epmd.service


epmd started successfully again.

So the problem seems to be that overriding epmd.socket with
"ListenStream=127.0.0.1:4369" causes a bind failure even when the port
is not in use.
It looks like either:

- the packaged systemd socket setup does not support this override
cleanly,
- the socket unit and service interaction is not behaving as expected,
- or there is some hidden conflict/state left behind by the existing
epmd setup.

System details:
- Debian 13
- epmd auto-installed by ejabberd (apt install ejabberd)

Expected behavior:
- epmd.socket should bind to 127.0.0.1:4369 successfully when the port
is free.

Actual behavior:
- epmd.socket fails with "Address already in use"
]