How do I troubleshoot Visual Studio .net core Windows 10 Docker containers with error "localhost took too long to respond" (ERR_CONNECTION_TIMED_OUT)?

Question

New to Docker / containers. Everything I've read and watched online shows that Docker for Windows "just works" with Visual Studio by adding the DockerFile to the project, and away it goes. I have a default/generated MVC.Net 6 (core) application (I added no logic of my own), and it runs just fine under the "IIS Express" mode. When I select the "Docker" mode, it appears to build ok, but then it times out when it tries to open the app in the browser. First it pops up a message in Visual Studio saying, "A remote operation is taking longer than expected", then another message pops up in Visual Studio saying, "The network connection to XXX.XX.XXX.XXX:XXXX has been lost. Debugging will be aborted". When I click OK, it opens a browser window (Chrome) to url http://localhost:0/. Turning off the firewall didn't help.

I've placed the "Container Tools" output from VS at the end of this description.

I left the DockerFile code itself as-is from what is generated by VS:

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
WORKDIR /app
EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
WORKDIR /src
COPY ["testingDocker.csproj", "."]
RUN dotnet restore "./testingDocker.csproj"
COPY . .
WORKDIR "/src/."
RUN dotnet build "testingDocker.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "testingDocker.csproj" -c Release -o /app/publish 
#/p:UseAppHost=false

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "testingDocker.dll"]

I have pulled a couple other sample images from Docker (eg, "markheath/samplewebapp:windows" and "kgpkgp/samplewebapp:latest"), ran each of them, mapping the desired ports, eg,

docker run -d -p 8081:80 --name ContainerName ImageName:TagName ping -t localhost

...and then opened them in the browser successfully, eg,

http://localhost:8081/

I have used various host ports with success for these pulled images, so I think I can rule out network and firewall issues.

When I look at the Docker Desktop display, the "testingdocker" image is there, and the "testingDocker" container is there, but stopped with a status of "EXITED (4294967295)". The "Open with browser" option does not appear under the ellipsis button. When I try to create a new container from the existing image using the command line (docker run -d -p 8083:80....), the container successfully is created and runs, and the "Open with browser" option is available; when I select it, the browser opens to http://localhost:8083/ but fails to load, displaying message "localhost took too long to respond" (ERR_CONNECTION_TIMED_OUT). I've second-guessed (and third-guessed, etc) everything. Any advice on what might be wrong here?

"Container Tools" output from VS:

========== Checking for Container Prerequisites ==========
Verifying that Docker Desktop is installed...
Docker Desktop is installed.
========== Verifying that Docker Desktop is running... ==========
Verifying that Docker Desktop is running...
Docker Desktop is running.
========== Verifying Docker OS ==========
Verifying that Docker Desktop's operating system mode matches the project's target operating system...
Docker Desktop's operating system mode matches the project's target operating system.
========== Pulling Required Images ==========
Checking for missing Docker images...
Pulling Docker images. To cancel this download, close the command prompt window.
docker pull mcr.microsoft.com/dotnet/aspnet:6.0
Docker images are ready.
========== Warming up container(s) for testingDocker ==========
Starting up container(s)...
docker build -f "C:\J\testingDocker\testingDocker\Dockerfile" --force-rm -t testingdocker:dev --target base  --label "com.microsoft.created-by=visual-studio" --label "com.microsoft.visual-studio.project-name=testingDocker" "C:\J\testingDocker\testingDocker" 
Sending build context to Docker daemon  8.199MB

Step 1/5 : FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
 ---> 1eaec0f2abb1
Step 2/5 : WORKDIR /app
 ---> Running in d3b72aeec68e
Removing intermediate container d3b72aeec68e
 ---> 3f573ca3d231
Step 3/5 : EXPOSE 8080
 ---> Running in a880a99ebd54
Removing intermediate container a880a99ebd54
 ---> 22255aa22f3f
Step 4/5 : LABEL com.microsoft.created-by=visual-studio
 ---> Running in 58b503e11d66
Removing intermediate container 58b503e11d66
 ---> 41c0305f94a5
Step 5/5 : LABEL com.microsoft.visual-studio.project-name=testingDocker
 ---> Running in 3dea4d690e3c
Removing intermediate container 3dea4d690e3c
 ---> d05c6888e64f
Successfully built d05c6888e64f
Successfully tagged testingdocker:dev

Use 'docker scan' to run Snyk tests against images to find vulnerabilities and learn how to fix them
docker rm -f 2319c1e877821720d122cd45ee01c27cabf410acee68d41528e691a19e1bc8c5
2319c1e877821720d122cd45ee01c27cabf410acee68d41528e691a19e1bc8c5
docker run -dt -v "C:\Users\James\onecoremsvsmon\17.3.10630.1389:C:\remote_debugger:ro" -v "C:\J\testingDocker\testingDocker:C:\app" -v "C:\J\testingDocker\testingDocker:c:\src" -v "C:\Users\James\.nuget\packages\:c:\.nuget\fallbackpackages2" -v "C:\Program Files (x86)\Microsoft Visual Studio\Shared\NuGetPackages:c:\.nuget\fallbackpackages" -e "ASPNETCORE_LOGGING__CONSOLE__DISABLECOLORS=true" -e "ASPNETCORE_ENVIRONMENT=Development" -e "DOTNET_USE_POLLING_FILE_WATCHER=1" -e "NUGET_PACKAGES=c:\.nuget\fallbackpackages2" -e "NUGET_FALLBACK_PACKAGES=c:\.nuget\fallbackpackages;c:\.nuget\fallbackpackages2" -P --name testingDocker_1 --entrypoint C:\remote_debugger\x64\msvsmon.exe testingdocker:dev /noauth /anyuser /silent /nostatus /noclrwarn /nosecuritywarn /nofirewallwarn /nowowwarn /fallbackloadremotemanagedpdbs /timeout:2147483646 /LogDebuggeeOutputToStdOut 
51a6d9e31decdc7adf618d8cadbe09ef26e3aa19c13a7d63f13353761a333f89
Container started successfully.
========== Finished ==========

Answer 1

You can try below methods:

1. Check whether you have used networking security software. You can disable or close those application.

2. You can use DebugDiag Tools to monitor devenv.exe and msvsmon.exe , and collect the dump files.