Unable to connect to service in a docker container

Question

I have a created a .net 5 based service. This service works well locally. I am trying to put this into a docker container. However I am unable to connect to it. Service is running using Kestrel configured for 8080

My Dockerfile is fairly straight forward

FROM mcr.microsoft.com/dotnet/aspnet:5.0 #msft image

COPY ./bin/debug/net5.0/ .        #local items

EXPOSE 8080
ENTRYPOINT [dotnet, myservice.dll]

Command used to run the service

docker run -it -p 8080:8080 myservice

I have created an image and when I run the above image with -it flag I can see the service is executed. On inspecting/exporting of the container I can also see some application log files generated, indicating service is running successfully. When I run the swagger endpoint by executing curl inside container I do get the swagger UI HTML page.

However when I run this from my actual machine it doesn't seem to connect to any of the endpoints. I have run the image using -p 8080:8080 so it should respond on same port. I have tried using random local port maps, so certainly ports are not blocked.

I have also checked running another container based services on port 8080 but I am able to access the same, so definitely port is not blocked.

Not sure what am I missing here. Setup is pretty simple since its just a dummy service for testing with one swagger endpoint and another weatherforecast endpoint that comes with .net template.

Answer 1

By default the container will be listening internally on port 80 unless you have overridden that using the ASPNETCORE_URLS environment variable. EXPOSE in the Docker file doesn't do anything but document the ports intended to be used.

Try to run it with -p 8080:80 which will map port 8080 on the local machine to port 80 in the container.