Docker dotnet run port not mapping, windows 10 host, linux container - powershell

Question

I'm following a https://app.pluralsight.com/library/courses/docker-web-development/table-of-contents which uses the older microsoft/aspnetcore-build image but I'm running core 2.1 so I'm using microsoft/dotnet:2.1-sdk instead.
The command I'm running is:
docker run -it -p 8080:5001 -v ${pwd}:/app -w "/app"
microsoft/dotnet:2.1-sdk
and then once inside the TTY I do a dotnet run which gives me the following output:
Using launch settings from /app/Properties/launchSettings.json...
info:
Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[0]
User profile is available. Using '/root/.aspnet/DataProtection-Keys'
as key repository; keys will not be encrypted at rest.
info:
Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[58]
Creating key {5445e854-c1d9-4261-82f4-0fc3a7543e0a} with creation date
2018-12-14 10:41:13Z, activation date 2018-12-14 10:41:13Z, and
expiration date 2019-03-14 10:41:13Z.
warn:
Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
No XML encryptor configured. Key
{5445e854-c1d9-4261-82f4-0fc3a7543e0a} may be persisted to storage in
unencrypted form.
info:
Microsoft.AspNetCore.DataProtection.Repositories.FileSystemXmlRepository[39]
Writing data to file
'/root/.aspnet/DataProtection-Keys/key-5445e854-c1d9-4261-82f4-0fc3a7543e0a.xml'.
warn: Microsoft.AspNetCore.Server.Kestrel[0]
Unable to bind to https://localhost:5001 on the IPv6 loopback
interface: 'Cannot assign requested address'.
warn: Microsoft.AspNetCore.Server.Kestrel[0]
Unable to bind to http://localhost:5000 on the IPv6 loopback
interface: 'Cannot assign requested address'.
Hosting environment: Development
Content root path: /app
Now listening on: https://localhost:5001
Now listening on: http://localhost:5000
Application started. Press Ctrl+C to shut down.
Then, when I open browser on my host and navigate to http://localhost:8080 I get a "This page isn't working" "localhost didn't send any data" " ERR_EMPTY_RESPONSE"
I've tried a couple different port combinations too with the same result.
Can anyone spot where I went wrong? Or have any ideas / suggestions?

Answer 1

Not sure if this question still relevant for you, but I also encountered this issue and left my solution here for others. I used PowerShell with the next docker command (almost the same as your command, just used internal port 90 instead of 5000 and used --rm switch which will automatically remove the container when it exits):
docker run --rm -it -p 8080:90 -v ${pwd}:/app -w "/app" microsoft/dotnet /bin/bash
And after that, I got the interactive bash shell, and when typing dotnet run I got the same output as you and cannot reach my site in the container via localhost:8080.
I resolved it by using UseUrls method or --urls command-line argument. They (UseUrls method or --urls command-line argument) indicates the IP addresses or host addresses with ports and protocols that the server should listen on for requests. Below descriptions of solutions which worked for me:
Edit CreateWebHostBuildermethod in Program.cs like below:
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
.UseUrls("http://+:90") //for your case you should use 5000 instead of 90
.UseStartup<Startup>();
You can specify several ports if needed using the next syntax .UseUrls("http://+:90;http://+:5000")
With this approach, you just typed dotnet run in bash shell and then your container will be reachable with localhost:8080.
But with the previous approach you alter the default behavior of your source code, which you can forget and then maybe should debug and fix in the future. So I prefer 2nd approach without changing the source code. After typing docker command and getting an interactive bash shell instead of just dotnet run type it with --urls argument like below (in your case use port 5000 instead of 90):
dotnet run --urls="http://+:90"
In the documentation there is also a 3rd approach where you can use ASPNETCORE_URLS environment variable, but this approach didn't work for me. I used the next command (with -e switch):
docker run --rm -it -p 8080:90 -v ${pwd}:/app -w "/app" -e "ASPNETCORE_URLS=http://+:90" microsoft/dotnet /bin/bash
If you type printenv in bash you will see that ASPNETCORE_URLS environment variable was passed to the container, but for some reason dotnet run is ignoring it.