Cannot connect to docker port forwarding any port

Question

OS: Ubuntu 20.04 LTS

Docker version 20.10.7, build 20.10.7-0ubuntu1~20.04.2

Tried this (minimal way to reproduce), the previous day it works normally:

docker run --name nginx1 -p 8089:80 -d nginx:alpine

Works normally:

docker ps

CONTAINER ID   IMAGE          COMMAND                  CREATED         
74faabf44b8e   nginx:alpine   "/docker-entrypoint.…"   5 minutes ago   

STATUS         PORTS                                       NAMES
Up 5 minutes   0.0.0.0:8089->80/tcp, :::8089->80/tcp       nginx1

curl inside docker works:

docker exec -it 74faabf44b8e sh

/ # curl localhost
<!DOCTYPE html>
<html>
<head>
....

But when accessed from the host:

netstat -antpel | grep 8089
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
tcp        0      0 0.0.0.0:8089            0.0.0.0:*               LISTEN      0          82748695   -                   
tcp6       0      0 :::8089                 :::*                    LISTEN      0          82751546   - 

curl -v localhost:8089
*   Trying 127.0.0.1:8089...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8089 (#0)
> GET / HTTP/1.1
> Host: localhost:8089
> User-Agent: curl/7.68.0
> Accept: */*
> 
--> stuck without a response, after a while:
* Recv failure: Connection reset by peer
* Closing connection 0
curl: (56) Recv failure: Connection reset by peer

What's the possible cause of this?
This also doesn't work for another container (PostgreSQL), seems the docker-proxy does not forward back the response from docker?

already tried:

reinstall docker.io
delete all containers and re-create
docker network prune

Does localhost resolve to e.g. 127.0.0.1 on your machine? What does nslookup localhost return or cat /etc/hosts? What happens if you curl -v 127.0.0.1:8089? — DazWilkin
– DazWilkin, Commented Oct 5, 2021 at 19:45
I think Alpine does not include bash so it's curious that your docker exec works (using bash) on an Alpine image (unless it's aliased?) — DazWilkin
– DazWilkin, Commented Oct 5, 2021 at 19:46
yes, localhost = 127.0.0.1 on my machine ping localhost PING localhost (127.0.0.1) 56(84) bytes of data. 64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.039 ms @DazWilkin the result is connection result by peer after a while — Kokizzu
– Kokizzu, Commented Oct 5, 2021 at 20:13

Edouard Barthélémy · Accepted Answer · 2022-07-27 14:35:40Z

5

Ubuntu version: 22.04 LTS

Docker version: 20.10.17, build 100c701

Installation procedure: https://docs.docker.com/engine/install/ubuntu/

I am encountering the same problem as you on more recent versions of Ubuntu & Docker: Everything seems to be working fine except that the host is not able to reach the container on port, as defined by the -p <docker-host-port>:<docker-container-port> option.

curl http://localhost:<port> works from within the container, but not from outside despite port binding ...

I tried to restart docker daemon, restart machine, remove container, recreate container, remove image, recreate image, uninstall completely docker, reinstall docker from scratch. I just don't understand why Docker is acting funky like this on this specific instance (Ubuntu 22.04 + Docker).

edited Jul 27, 2022 at 14:35

answered Jul 27, 2022 at 3:29

Edouard Barthélémy

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2 Comments

Edouard Barthélémy Over a year ago

I just tried on a different physical machine running: Ubuntu version: 20.04.4 LTS (previous Ubuntu LTS version) and Docker version: 20.10.17, build 100c701 (same Docker version). Everything works as expected! That tells me that there is a problem, either with Ubuntu 22.04 LTS, or with the first physical machine (hardware?).

Edouard Barthélémy Over a year ago

On the first physical machine (Ubuntu version: 22.04 LTS, Docker version: 20.10.17, build 100c701), the curl http://localhost:<port> was returning me curl: (56) Recv failure: Connection reset by peer. I looked into that error, and thanks to this stackoverflow.com/questions/10285700/…, I found out that it was a VPN issue. Probably something that has to do with MTU (Maximum Transmission Unit) size of packets ... So, when disabling VPN, http://localhost:<port> is reachable via curl, and accessible via web browser.

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