c# - Kestrel port is always in use

Question

I'm using VSCode to develop an ASP.NET Core 5.0 application on Docker. I'm using the default Kestrel webserver behing an Nginx reverse proxy.

When I want to run the app, using docker-compose build and docker-compose up the app runs with a message saying that deployed apps cannot be run in development environment. Alright so I tried to run the app in debug with VSCode.

The problem is that whichever port I specify in the config, Kestrel will shoot an error saying

Failed to bind to address http://127.0.0.1:*port*: address already in use.

Name a port, any port, it will give an error. Given that it kinda works in docker-compose mode, I suspect the tasks.json file, or maybe the app is double-launched.

I ensured that all containers were stopped before launching in debug. I even did a docker system prune -a to start with a fresh environment. Nothing take this error out of the way.

Here are some config files :

launch.json

"preLaunchTask": "docker-run: debug"

tasks.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "build",
            "command": "dotnet",
            "type": "process",
            "args": [
                "build",
                "${workspaceFolder}/app/app.csproj",
                "/property:GenerateFullPaths=true",
                "/consoleloggerparameters:NoSummary"
            ],
            "problemMatcher": "$msCompile"
        },
        {
            "label": "docker-build: debug",
            "type": "docker-build",
            "dependsOn": [
                "build"
            ],
            "dockerBuild": {
                "tag": "appnet_app:dev",                
                "target": "base",
                "dockerfile": "${workspaceFolder}/app/Dockerfile",
                "context": "${workspaceFolder}/app",
                "pull": true
            },
            "netCore": {
                "appProject": "${workspaceFolder}/app/app.csproj"
            },
            "options": {            
                "env": {
                    "ASPNETCORE_ENVIRONMENT": "Development"
                }
            }
        },
        {
            "label": "docker-run: debug",
            "type": "docker-run",
            "dependsOn": [
                "docker-build: debug" 
            ],
            "dockerRun": {
                "env": {
                    "ASPNETCORE_ENVIRONMENT":"Development" 
                },
                "image": "appnet_app:dev"
            },
            "netCore": {
                "appProject": "${workspaceFolder}/app/app.csproj",
                "enableDebugging": true
            },
            "options": {
                "env": {
                    "ASPNETCORE_ENVIRONMENT": "Development"
                }
            }
        }
    ]
}

app Dockerfile

FROM mcr.microsoft.com/dotnet/aspnet:5.0-buster-slim as base
 
WORKDIR /app
COPY bin/Debug/net5.0 .
 
ENV ASPNETCORE_URLS=http://+:8000
EXPOSE 8000
 
ENTRYPOINT ["dotnet", "app.dll"]

I also have a launchSettings.json in Properties directory, which I'm quite confused which file is used between this one and the launch.json

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:4324",
      "sslPort": 5356
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "app": {
      "commandName": "Project",
      "dotnetRunMessages": "true",
      "launchBrowser": true,
      "applicationUrl": "http://localhost:8000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

Program.cs

public static void Main(string[] args)
{
    CreateHostBuilder(args).Build().Run();   // <----- Crashes on this line
}

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();                    
            webBuilder.UseUrls("http://localhost:8000");
        });

question from:https://stackoverflow.com/questions/65861998/kestrel-port-is-always-in-use

Answer 1

Waitting for answers