Connection reset by peer when when hitting Docker container

Question

I'm having a problem, where I can't send network requests to a Docker container I've created. I've exposed the correct ports, so I'm not sure what other issues could be at fault here.

I have a server running in container alice at localhost:10009:

$ docker exec -it alice bash bash-4.4# curl localhost:10009 curl: (52) Empty reply from server 

Port 10009 is exposed from my container:

$ docker port alice  10009/tcp -> 0.0.0.0:10009 

When doing the same curl from my host machine I get a different message:

$ curl localhost:10009 curl: (56) Recv failure: Connection reset by peer 

Answer 1

I would check to see if the server application is configured to only listen to requests coming from its "localhost", this check depends on the type of server that you're using which is not mentioned.

an easy check is to start your container as follows:

docker run --network host -d yourimagename 

You don't need to worry about port mapping since you're using the host network

then try to curl, if that works, then you'll just need to review your server listening IP setting.

curl localhost:10009 

Answer 2

I think there are some problems with @Bouzid Zitouni's answer, according to Docker official documentation:

this is the same level of isolation as if the nginx process were running directly on the Docker host and not in a container

However, if you use the --network host you will not have isolated networking in the container, and the host networking driver only works on Linux hosts.

The problem of Connection refused/reset happens because your Server is listening on 127.0.0.1 inside the container and the port forwarding is going to external IP of the container (e.g. 172.17.0.2).

Solution

In your case you need to run a new container making your server to listen on all interfaces. Example using python http.server :

docker run -p 8000:8000 -it python:3.7-slim python3 -m http.server --bind 0.0.0.0 

Note

The option --bind 0.0.0.0 it's specific option of http.server. Probally your server has other ways to specify this.

References:

https://pythonspeed.com/articles/docker-connection-refused/

https://docs.docker.com/network/network-tutorial-host/