What does "Now listening on: http://[::]:80" mean?

Question

Have created an dotnet core application and when run the command:

docker-compose up

everything goes well but I don't understand what does the below line mean:

Now listening on: http://[::]:80

Dockerfile content is:

FROM microsoft/aspnetcore:2.0
ARG source 
WORKDIR /app 
EXPOSE 80 
COPY ${source:-obj/Docker/publish} . 
ENTRYPOINT ["dotnet", "SampleCoreApp.dll"]

docker-compose file is:

version: '3'
services:
 samplecoreapp:
   image: samplecoreapp
   build:
     context: ./SampleCoreApp
     dockerfile: Dockerfile

Why is that I'm not seeing the IP address?

If i have a 3 VMs and if I want to run this application on VM2 then how can I deploy this docker container to VM2?

Answer 1

Now listening on: http://[::]:80

means: your application is telling you that it is listening on TCP port 80 on all IPv6 addresses it owns.

[::] is the short-hand notation for the IPv6 address 0000:0000:0000:0000:0000:0000:0000:0000 within an URL. Note that :: is not a valid IPv6 address, but often is used as an alias for "all my IPv6 addresses".

Similarly, a web server that listens on TCP port 80 of all its IPv4 addresses usually reports that it is listening on http://0.0.0.0:80. In your case, it seems to be expecting IPv6 traffic instead. However, many applications are dual stack and listen to both, IPv4 and IPv6.