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dockerport

How do I debug docker port mapping?

I'm stuck with getting port mapping to work with a docker instance I've built. curl localhost in the docker container shows the application is working fine, but curl from host returns:

* Rebuilt URL to: 127.0.0.1/
* Hostname was NOT found in DNS cache
*   Trying 127.0.0.1...
* Connected to 127.0.0.1 (127.0.0.1) port 80 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.35.0
> Host: 127.0.0.1
> Accept: */*
> 
* Empty reply from server
* Connection #0 to host 127.0.0.1 left intact
curl: (52) Empty reply from server

I've exposed the port with -p flag. I've tried mapping all sorts of different ports. How might I debug this? What are common problems with port mapping?

Solution

  • If you're doing curl outside of the container - it won't work. If I understand you correctly then you have several variants:

    1. Use command docker inspect --format='{{range $p, $conf := .NetworkSettings.Ports}} {{$p}} -> {{(index $conf 0).HostPort}} {{end}}' $INSTANCE_ID - more on Docker Inspect.

    2. Use command docker port $CONTAINER_NAME - more on Docker Port.

    Execute command docker inspect -f '{{ .NetworkSettings.IPAddress }}' <CONTAINER_NAME>. It should show you internal IP-address and then try to curl <IP_FROM_COMMAND>:<PORT>.