问题描述：
在Mac OS本地Rider IDE运行c# ASP.Net 代码时，Log如下：
info: Microsoft.Hosting.Lifetime[0]
Now listening on: https://localhost:5001
info: Microsoft.Hosting.Lifetime[0]
Now listening on: http://localhost:5000
info: Microsoft.Hosting.Lifetime[0]
https://localhost:5001/swagger/index.html
自动打开的Swagger页面也可以正常访问。
但如果使用docker image
docker build -f ./Dockerfile -t "image:latest" "$(pwd)"
docker run --rm -p 8080:5001 image:latest
结果在运行时会显示：
Now listening on: http://[::]:80
访问https://localhost:8080/swagger/index.html
结果得到了Error:
“This page isn’t working – localhost didn’t send any data.”
ERR_EMPTY_RESPONSE
or
“This site can’t be reached – localhost unexpectedly closed the connection.”
ERR_CONNECTION_CLOSED
使用的Dockerfile如下：
FROM mcr.microsoft.com/dotnet/sdk:5.0 AS build
WORKDIR /App
# Copy everything else and build
COPY /ExampleaApp/. .
RUN dotnet publish -c release -o publish
#Build runtime image
FROM mcr.microsoft.com/dotnet/runtime:5.0
FROM mcr.microsoft.com/dotnet/aspnet:5.0
WORKDIR /App
COPY --from=build /App/publish .
EXPOSE 5001
ENTRYPOINT ["dotnet", "ExampleApp.dll"]
原因分析：
mcr.microsoft.com/dotnet/aspnet 在默认状态下设置ASPNETCORE_URLS环境变量为http://+:80，如果在没有通过Program.cs中的app.UseUrl在app中设定URL，那么app就会在容器中监听port 80。
尝试把Dockerfile中EXPOSE 5001改成EXPOSE 80，然后运行如下命令：
docker rmi $(docker image ls -aq)
docker build -f ./Dockerfile -t "mega-images:latest" "$(pwd)"
docker run --rm -p 8080:80 mega-images:latest
仍旧访问https://localhost:8080/swagger/index.html
得到以下Error:
“This site can’t provide a secure connection – localhost sent an invalid response.”
ERR_SSL_PROTOCOL_ERROR
尝试着在本地Terminal运行DockerFile中的dotnet publish和dotnet ExampleApp.dll命令:
dotnet publish -c release -o publish
cd publish
dotnet ExampleApp.dll
Log如下：
info: Microsoft.Hosting.Lifetime[0]
Now listening on: http://localhost:5000
info: Microsoft.Hosting.Lifetime[0]
Now listening on: https://localhost:5001
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Production
访问https://localhost:5001/swagger/index.html
得到Error：
“This localhost page can’t be found”
HTTP ERROR 404
访问https://localhost:5000/swagger/index.html
得到Error：
“This site can’t provide a secure connection”
ERR_SSL_PROTOCOL_ERROR
解决方案：
检查了Rider IDE： Run -> Edit Configurations…
发现如下Environment Variables：
ASPNETCORE_URLS=https://localhost:5001;http://localhost:5000 ASPNETCORE_ENVIRONMENT=Development
这些环境变量来自于Mega/Properties/launchSettings.json(launchSettings.json file already contains the entries for default URLs i.e. http://localhost:5000 & https://localhost:5001 in project settings.)
类似的，可以在本地Mac terminal中设置相同的环境变量：
export "ASPNETCORE_URLS=https://localhost:5001;http://localhost:5000"
export "ASPNETCORE_ENVIRONMENT=Development"
(HTTPS:5001, HTTP: 5000)
再次运行dotnet Example.dll
访问https://localhost:5000/swagger/index.html，得到Error：
ERR_SSL_PROTOCOL_ERROR
访问https://localhost:5001/swagger/index.html，Swagger页面可以正常访问。
在Dockerfile中加入：
ENV ASPNETCORE_ENVIRONMENT=Development
ENV ASPNETCORE_URLS=http://+:5001;http://+:5000
EXPOSE 5001
EXPOSE 5000
运行命令：
docker rmi $(docker image ls -aq)
docker build -f ./Dockerfile -t "mega-images:latest" "$(pwd)"
docker run --rm -p 8080:80 mega-images:latest
然后就可以访问Docker container中的ASP.Net app啦： http://localhost:8080/swagger/index.html
参考资料： https://stackoverflow.com/questions/48669548/why-does-aspnet-core-start-on-port-80-from-within-docker
