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Unable to contact postgres runnign nunning on host

Hi,
This is driving me nuts.
I am using rootless docker.

I have a very simple container. All it does is try to connect to a postgresql database and do a simple select.
This simple application works flawlessly outside of a container.

Inside the container it complains about unable to connect.

docker0 interface has ip 172.17.0.1 and that is where I try to connect to from the container.
Simple bridged network.

netstat shows me that postgres is indeed listening on the 172.17.0.1 interface and accepts the 172.17.0.0/16 network

firewall shows that forwarding is allowed.
firewall has been configured to allow all traffic from 172.17.0.0/16

kernel forwarding is on

still no joy. postgresql logs connection attempts but shows nothing when running the container.

running another container and doing a shell inside the container and installing the postgresql-client also says
error: could not connect to server: Connection refused

telnet to 172.17.0.1 5432 gives no connection.

What am I doing wrong or not seeing?

Any and all hints and help is greatly appreciated.

Regards,
Jeroen Baten

Other example. same result:

$ nc -l 8020 &
[1] 10835

$ docker run -ti --network=“host” alpine /bin/sh
/ # apk add curl
fetch https://dl-cdn.alpinelinux.org/alpine/v3.13/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.13/community/x86_64/APKINDEX.tar.gz
(1/5) Installing ca-certificates (20191127-r5)
(2/5) Installing brotli-libs (1.0.9-r3)
(3/5) Installing nghttp2-libs (1.42.0-r1)
(4/5) Installing libcurl (7.74.0-r1)
(5/5) Installing curl (7.74.0-r1)
Executing busybox-1.32.1-r2.trigger
Executing ca-certificates-20191127-r5.trigger
OK: 8 MiB in 19 packages
/ # curl localhost:8020
curl: (7) Failed to connect to localhost port 8020: Connection refused
/ #