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Nov 02, 2006 Mac Pro 2.66Ghz Mac OS X (10.4.8) Powerbook G4 1.33Ghz. Nov 2, 2006 4:11 PM. You can also use minicom, a CLI app, to talk to the serial port.

By Rick Anderson and Kirk Larkin

ASP.NET Core configures app behavior based on the runtime environment using an environment variable.

View or download sample code (how to download)

Environments

To determine the runtime environment, ASP.NET Core reads from the following environment variables:

1. ASPNETCORE_ENVIRONMENT when ConfigureWebHostDefaults is called. The default ASP.NET Core web app templates call ConfigureWebHostDefaults. The ASPNETCORE_ENVIRONMENT value overrides DOTNET_ENVIRONMENT.

IHostEnvironment.EnvironmentName can be set to any value, but the following values are provided by the framework:

• Development : The launchSettings.json file sets ASPNETCORE_ENVIRONMENT to Development on the local machine.
• Production : The default if DOTNET_ENVIRONMENT and ASPNETCORE_ENVIRONMENT have not been set.

The following code:

• Calls UseDeveloperExceptionPage when ASPNETCORE_ENVIRONMENT is set to Development.
• Calls UseExceptionHandler when the value of ASPNETCORE_ENVIRONMENT is set to Staging, Production, or Staging_2.
• Injects IWebHostEnvironment into Startup.Configure. This approach is useful when the app only requires adjusting Startup.Configure for a few environments with minimal code differences per environment.
• Is similar to the code generated by the ASP.NET Core templates.

The Environment Tag Helper uses the value of IHostEnvironment.EnvironmentName to include or exclude markup in the element:

The About page from the sample code includes the preceding markup and displays the value of IWebHostEnvironment.EnvironmentName.

On Windows and macOS, environment variables and values aren't case-sensitive. Linux environment variables and values are case-sensitive by default.

Create EnvironmentsSample

The sample code used in this document is based on a Razor Pages project named EnvironmentsSample.

The following code creates and runs a web app named EnvironmentsSample:

When the app runs, it displays some of the following output:

Development and launchSettings.json

The development environment can enable features that shouldn't be exposed in production. For example, the ASP.NET Core templates enable the Developer Exception Page in the development environment.

The environment for local machine development can be set in the PropertieslaunchSettings.json file of the project. Environment values set in launchSettings.json override values set in the system environment.

The launchSettings.json file:

• Is only used on the local development machine.
• Is not deployed.
• contains profile settings.

The following JSON shows the launchSettings.json file for an ASP.NET Core web projected named EnvironmentsSample created with Visual Studio or dotnet new:

The preceding markup contains two profiles:

• IIS Express: The default profile used when launching the app from Visual Studio. The 'commandName' key has the value 'IISExpress', therefore, IISExpress is the web server. You can set the launch profile to the project or any other profile included. For example, in the image below, selecting the project name launches the Kestrel web server.

• EnvironmentsSample: The profile name is the project name. This profile is used by default when launching the app with dotnet run. The 'commandName' key has the value 'Project', therefore, the Kestrel web server is launched.

The value of commandName can specify the web server to launch. commandName can be any one of the following:

• IISExpress : Launches IIS Express.
• IIS : No web server launched. IIS is expected to be available.
• Project : Launches Kestrel.

The Visual Studio project properties Debug tab provides a GUI to edit the launchSettings.json file. Changes made to project profiles may not take effect until the web server is restarted. Kestrel must be restarted before it can detect changes made to its environment.

The following launchSettings.json file contains multiple profiles:

Profiles can be selected:

• From the Visual Studio UI.

• Using the dotnet run command in a command shell with the --launch-profile option set to the profile's name. This approach only supports Kestrel profiles.

Warning

launchSettings.json shouldn't store secrets. The Secret Manager tool can be used to store secrets for local development.

When using Visual Studio Code, environment variables can be set in the .vscode/launch.json file. The following example sets several Host configuration values environment variables:

The .vscode/launch.json file is only used by Visual Studio Code.

Production

The production environment should be configured to maximize security, performance, and application robustness. Some common settings that differ from development include:

• Caching.
• Client-side resources are bundled, minified, and potentially served from a CDN.
• Diagnostic error pages disabled.
• Friendly error pages enabled.
• Production logging and monitoring enabled. For example, using Application Insights.

Set the environment

It's often useful to set a specific environment for testing with an environment variable or platform setting. If the environment isn't set, it defaults to Production, which disables most debugging features. The method for setting the environment depends on the operating system.

When the host is built, the last environment setting read by the app determines the app's environment. The app's environment can't be changed while the app is running.

The About page from the sample code displays the value of IWebHostEnvironment.EnvironmentName.

Azure App Service

To set the environment in Azure App Service, perform the following steps:

1. Select the app from the App Services blade.
2. In the Settings group, select the Configuration blade.
3. In the Application settings tab, select New application setting.
4. In the Add/Edit application setting window, provide ASPNETCORE_ENVIRONMENT for the Name. For Value, provide the environment (for example, Staging).
5. Select the Deployment slot setting check box if you wish the environment setting to remain with the current slot when deployment slots are swapped. For more information, see Set up staging environments in Azure App Service in the Azure documentation.
6. Select OK to close the Add/Edit application setting window.
7. Select Save at the top of the Configuration blade.

Azure App Service automatically restarts the app after an app setting is added, changed, or deleted in the Azure portal.

Windows

Environment values in launchSettings.json override values set in the system environment.

To set the ASPNETCORE_ENVIRONMENT for the current session when the app is started using dotnet run, the following commands are used:

Command prompt

PowerShell

The preceding command sets ASPNETCORE_ENVIRONMENT only for processes launched from that command window.

To set the value globally in Windows, use either of the following approaches:

• Open the Control Panel > System > Advanced system settings and add or edit the ASPNETCORE_ENVIRONMENT value:

• Open an administrative command prompt and use the setx command or open an administrative PowerShell command prompt and use [Environment]::SetEnvironmentVariable:

  Command prompt

  The /M switch indicates to set the environment variable at the system level. If the /M switch isn't used, the environment variable is set for the user account.

  PowerShell

  The Machine option value indicates to set the environment variable at the system level. If the option value is changed to User, the environment variable is set for the user account.

When the ASPNETCORE_ENVIRONMENT environment variable is set globally, it takes effect for dotnet run in any command window opened after the value is set. Environment values in launchSettings.json override values set in the system environment.

web.config

To set the ASPNETCORE_ENVIRONMENT environment variable with web.config, see the Setting environment variables section of ASP.NET Core Module.

Project file or publish profile

For Windows IIS deployments: Include the <EnvironmentName> property in the publish profile (.pubxml) or project file. This approach sets the environment in web.config when the project is published:

Per IIS Application Pool

To set the ASPNETCORE_ENVIRONMENT environment variable for an app running in an isolated Application Pool (supported on IIS 10.0 or later), see the AppCmd.exe command section of the Environment Variables <environmentVariables> topic. When the ASPNETCORE_ENVIRONMENT environment variable is set for an app pool, its value overrides a setting at the system level.

When hosting an app in IIS and adding or changing the ASPNETCORE_ENVIRONMENT environment variable, use any one of the following approaches to have the new value picked up by apps:

• Execute net stop was /y followed by net start w3svc from a command prompt.
• Restart the server.

macOS

Setting the current environment for macOS can be performed in-line when running the app:

Alternatively, set the environment with export prior to running the app:

Machine-level environment variables are set in the .bashrc or .bash_profile file. Edit the file using any text editor. Add the following statement:

Linux

For Linux distros, use the export command at a command prompt for session-based variable settings and bash_profile file for machine-level environment settings.

Set the environment in code

Call UseEnvironment when building the host. See .NET Generic Host.

Configuration by environment

To load configuration by environment, see Configuration in ASP.NET Core.

Environment-based Startup class and methods

Inject IWebHostEnvironment into the Startup class

Inject IWebHostEnvironment into the Startup constructor. This approach is useful when the app requires configuring Startup for only a few environments with minimal code differences per environment.

In the following example:

• The environment is held in the _env field.
• _env is used in ConfigureServices and Configure to apply startup configuration based on the app's environment.

Startup class conventions

When an ASP.NET Core app starts, the Startup class bootstraps the app. The app can define multiple Startup classes for different environments. The appropriate Startup class is selected at runtime. The class whose name suffix matches the current environment is prioritized. If a matching Startup{EnvironmentName} class isn't found, the Startup class is used. This approach is useful when the app requires configuring startup for several environments with many code differences per environment. Typical apps will not need this approach.

To implement environment-based Startup classes, create a Startup{EnvironmentName} classes and a fallback Startup class:

Use the UseStartup(IWebHostBuilder, String) overload that accepts an assembly name:

Startup method conventions

Configure and ConfigureServices support environment-specific versions of the form Configure<EnvironmentName> and Configure<EnvironmentName>Services. This approach is useful when the app requires configuring startup for several environments with many code differences per environment:

Additional resources

By Rick Anderson

ASP.NET Core configures app behavior based on the runtime environment using an environment variable.

View or download sample code (how to download)

Environments

ASP.NET Core reads the environment variable ASPNETCORE_ENVIRONMENT at app startup and stores the value in IHostingEnvironment.EnvironmentName. ASPNETCORE_ENVIRONMENT can be set to any value, but three values are provided by the framework:

• Production (default)

The preceding code:

• Calls UseDeveloperExceptionPage when ASPNETCORE_ENVIRONMENT is set to Development.

• Calls UseExceptionHandler when the value of ASPNETCORE_ENVIRONMENT is set one of the following:

  • Staging
  • Production
  • Staging_2

The Environment Tag Helper uses the value of IHostingEnvironment.EnvironmentName to include or exclude markup in the element:

On Windows and macOS, environment variables and values aren't case-sensitive. Linux environment variables and values are case-sensitive by default.

Development

The development environment can enable features that shouldn't be exposed in production. For example, the ASP.NET Core templates enable the Developer Exception Page in the development environment.

The environment for local machine development can be set in the PropertieslaunchSettings.json file of the project. Environment values set in launchSettings.json override values set in the system environment.

The following JSON shows three profiles from a launchSettings.json file:

Note

The applicationUrl property in launchSettings.json can specify a list of server URLs. Use a semicolon between the URLs in the list:

When the app is launched with dotnet run, the first profile with 'commandName': 'Project' is used. The value of commandName specifies the web server to launch. commandName can be any one of the following:

• IISExpress
• IIS
• Project (which launches Kestrel)

When an app is launched with dotnet run:

• launchSettings.json is read if available. environmentVariables settings in launchSettings.json override environment variables.
• The hosting environment is displayed.

The following output shows an app started with dotnet run:

The Visual Studio project properties Debug tab provides a GUI to edit the launchSettings.json file:

Changes made to project profiles may not take effect until the web server is restarted. Kestrel must be restarted before it can detect changes made to its environment.

Warning

launchSettings.json shouldn't store secrets. The Secret Manager tool can be used to store secrets for local development.

When using Visual Studio Code, environment variables can be set in the .vscode/launch.json file. The following example sets the environment to Development:

A .vscode/launch.json file in the project isn't read when starting the app with dotnet run in the same way as Properties/launchSettings.json. When launching an app in development that doesn't have a launchSettings.json file, either set the environment with an environment variable or a command-line argument to the dotnet run command.

Production

The production environment should be configured to maximize security, performance, and app robustness. Some common settings that differ from development include:

• Caching.
• Client-side resources are bundled, minified, and potentially served from a CDN.
• Diagnostic error pages disabled.
• Friendly error pages enabled.
• Production logging and monitoring enabled. For example, Application Insights.

Set the environment

It's often useful to set a specific environment for testing with an environment variable or platform setting. If the environment isn't set, it defaults to Production, which disables most debugging features. The method for setting the environment depends on the operating system.

When the host is built, the last environment setting read by the app determines the app's environment. The app's environment can't be changed while the app is running.

Environment variable or platform setting

Azure App Service

To set the environment in Azure App Service, perform the following steps:

1. Select the app from the App Services blade.
2. In the Settings group, select the Configuration blade.
3. In the Application settings tab, select New application setting.
4. In the Add/Edit application setting window, provide ASPNETCORE_ENVIRONMENT for the Name. For Value, provide the environment (for example, Staging).
5. Select the Deployment slot setting check box if you wish the environment setting to remain with the current slot when deployment slots are swapped. For more information, see Set up staging environments in Azure App Service in the Azure documentation.
6. Select OK to close the Add/Edit application setting window.
7. Select Save at the top of the Configuration blade.

Azure App Service automatically restarts the app after an app setting (environment variable) is added, changed, or deleted in the Azure portal.

Windows

To set the ASPNETCORE_ENVIRONMENT for the current session when the app is started using dotnet run, the following commands are used:

Command prompt

PowerShell

These commands only take effect for the current window. When the window is closed, the ASPNETCORE_ENVIRONMENT setting reverts to the default setting or machine value.

To set the value globally in Windows, use either of the following approaches:

• Open the Control Panel > System > Advanced system settings and add or edit the ASPNETCORE_ENVIRONMENT value:

• Open an administrative command prompt and use the setx command or open an administrative PowerShell command prompt and use [Environment]::SetEnvironmentVariable:

  Command prompt

  The /M switch indicates to set the environment variable at the system level. If the /M switch isn't used, the environment variable is set for the user account.

  PowerShell

  The Machine option value indicates to set the environment variable at the system level. If the option value is changed to User, the environment variable is set for the user account.

When the ASPNETCORE_ENVIRONMENT environment variable is set globally, it takes effect for dotnet run in any command window opened after the value is set.

web.config

To set the ASPNETCORE_ENVIRONMENT environment variable with web.config, see the Setting environment variables section of ASP.NET Core Module.

Project file or publish profile

For Windows IIS deployments: Include the <EnvironmentName> property in the publish profile (.pubxml) or project file. This approach sets the environment in web.config when the project is published:

Per IIS Application Pool

To set the ASPNETCORE_ENVIRONMENT environment variable for an app running in an isolated Application Pool (supported on IIS 10.0 or later), see the AppCmd.exe command section of the Environment Variables <environmentVariables> topic. When the ASPNETCORE_ENVIRONMENT environment variable is set for an app pool, its value overrides a setting at the system level.

Important

When hosting an app in IIS and adding or changing the ASPNETCORE_ENVIRONMENT environment variable, use any one of the following approaches to have the new value picked up by apps:

• Execute net stop was /y followed by net start w3svc from a command prompt.
• Restart the server.

macOS

Setting the current environment for macOS can be performed in-line when running the app:

Alternatively, set the environment with export prior to running the app:

Machine-level environment variables are set in the .bashrc or .bash_profile file. Edit the file using any text editor. Add the following statement:

Linux

For Linux distros, use the export command at a command prompt for session-based variable settings and bash_profile file for machine-level environment settings.

Set the environment in code

Call UseEnvironment when building the host. See ASP.NET Core Web Host.

Configuration by environment

To load configuration by environment, we recommend:

• appsettings files (appsettings.{Environment}.json). See Configuration in ASP.NET Core.
• Environment variables (set on each system where the app is hosted). See ASP.NET Core Web Host and Safe storage of app secrets in development in ASP.NET Core.
• Secret Manager (in the Development environment only). See Safe storage of app secrets in development in ASP.NET Core.

Environment-based Startup class and methods

Inject IHostingEnvironment into Startup.Configure

Inject IHostingEnvironment into Startup.Configure. This approach is useful when the app only requires configuring Startup.Configure for only a few environments with minimal code differences per environment.

Inject IHostingEnvironment into the Startup class

Inject IHostingEnvironment into the Startup constructor and assign the service to a field for use throughout the Startup class. This approach is useful when the app requires configuring startup for only a few environments with minimal code differences per environment.

In the following example:

• The environment is held in the _env field.
• _env is used in ConfigureServices and Configure to apply startup configuration based on the app's environment.

Startup class conventions

When an ASP.NET Core app starts, the Startup class bootstraps the app. The app can define separate Startup classes for different environments (for example, StartupDevelopment). The appropriate Startup class is selected at runtime. The class whose name suffix matches the current environment is prioritized. If a matching Startup{EnvironmentName} class isn't found, the Startup class is used. This approach is useful when the app requires configuring startup for several environments with many code differences per environment.

To implement environment-based Startup classes, create a Startup{EnvironmentName} class for each environment in use and a fallback Startup class:

Use the UseStartup(IWebHostBuilder, String) overload that accepts an assembly name:

Startup method conventions

Configure and ConfigureServices support environment-specific versions of the form Configure<EnvironmentName> and Configure<EnvironmentName>Services. This approach is useful when the app requires configuring startup for several environments with many code differences per environment.

Additional resources

How do I determine if a port is in use under Linux or Unix-like system? How can I verify which ports are listening on Linux server? How do I check if port is in use on Linux operating system using the CLI?
It is important you verify which ports are listening on the server’s network interfaces. You need to pay attention to open ports to detect an intrusion. Apart from an intrusion, for troubleshooting purposes, it may be necessary to check if a port is already in use by a different application on your servers. For example, you may install Apache and Nginx server on the same system. So it is necessary to know if Apache or Nginx is using TCP port # 80/443. This quick tutorial provides steps to use the netstat, nmap and lsof command to check the ports in use and view the application that is utilizing the port.

How to check if port is in use in

To check the listening ports and applications on Linux:

1. Open a terminal application i.e. shell prompt.
2. Run any one of the following command on Linux to see open ports:
   sudo lsof -i -P -n | grep LISTEN
   sudo netstat -tulpn | grep LISTEN
   sudo lsof -i:22 ## see a specific port such as 22 ##
   sudo nmap -sTU -O IP-address-Here
3. For the latest version of Linux use the ss command. For example, ss -tulw

Let us see commands and its output in details.

Option #1: lsof command

The syntax is:
$ sudo lsof -i -P -n
$ sudo lsof -i -P -n | grep LISTEN
$ doas lsof -i -P -n | grep LISTEN ### [OpenBSD] ###
Sample outputs:
Consider the last line from above outputs:

• sshd is the name of the application.
• 10.86.128.138 is the IP address to which sshd application bind to (LISTEN)
• 22 is the TCP port that is being used (LISTEN)
• 85379 is the process ID of the sshd process

Option #2: netstat command

You can check the listening ports and applications with netstat as follows.

Linux netstat syntax

Macos Determine App Using Port Phone

Run netstat command along with grep command to filter out port in LISTEN state:
$ netstat -tulpn | grep LISTEN
The netstat command deprecated for some time on Linux. Therefore, you need to use the ss command as follows:
sudo ss -tulw
sudo ss -tulwn

Where ss command options are as follows:

• -t : Show only TCP sockets on Linux
• -u : Display only UDP sockets on Linux
• -l : Show listening sockets. For example, TCP port 22 is opened by SSHD server.
• -p : List process name that opened sockets
• -n : Don’t resolve service names i.e. don’t use DNS

Related: Linux Find Out Which Process Is Listening Upon a Port

FreeBSD/MacOS X netstat syntax

$ netstat -anp tcp | grep LISTEN
$ netstat -anp udp | grep LISTEN

Macos Determine App Using Port Cable

OpenBSD netstat syntax

$ netstat -na -f inet | grep LISTEN
$ netstat -nat | grep LISTEN

Option #3: nmap command

The syntax is:
$ sudo nmap -sT -O localhost
$ sudo nmap -sU -O 192.168.2.13 ##[ list open UDP ports ]##
$ sudo nmap -sT -O 192.168.2.13 ##[ list open TCP ports ]##
Sample outputs:
You can combine TCP/UDP scan in a single command:
$ sudo nmap -sTU -O 192.168.2.13

A note about Windows users

You can check port usage from Windows operating system using following command:
netstat -bano | more
netstat -bano | grep LISTENING
netstat -bano | findstr /R /C:'[LISTEING]'


Macos Determine App Using Port Address

Conclusion

Best Macos Apps

This page explained command to determining if a port is in use on Linux or Unix-like server. For more information see the nmap command and lsof command page online here