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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

Answers

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