Introduction and Background
It has been a while since I wanted to write something about ASP.NET Core hosting stuff, and Kestrel was something that was interesting from my own perspective. Previously I have written a bunch of stuff to cover up the basics of ASP.NET Core programming and in this one I will guide you on hosting the ASP.NET Core application natively, using the .NET Core libraries that you download while installation process. Secondly, it has been a while since I have had written anything at all and I might have forgotten the interests of my readers so excuse me if I miss out a few things.
Figure 1: Image captured from Scott Hanselman’s blog.
There is a lot of stuff to share in this post today, so stay tuned and hold your breath basically. I will be covering the following steps in this article:
- Installation of the latest version of .NET Core on Linux environment
- If you already have a .NET Core framework installed, upgrade your system if that doesn’t support ASP.NET programming as of now.
- In the previous versions, web development wasn’t support in .NET Core for Linux operating systems. In the recent versions, it has been added to the recent versions now so that is why I insist that before continuing you at least install the latest version of .NET Core.
- Setup an ASP.NET Web Application in your Linux environment.
- I will guide you through many stages, such as development, editing, maintenance and using an IDE for all of these things.
- I will walk you through many different areas (not the ASP.NET Area!) in ASP.NET web application’s file hierarchy, plus I will tell you what is back and what is about to change (or subject to change in the hierarchy).
- Build and run the project
- In this section, I will guide you through a few of the tips that would deem helpful to you.
- Before running, I will give you an overview of Kestrel — web server for ASP.NET 5.
- I will then move onwards to using the website, which has the same feel as it had in Windows operating system, while developing ASP.NET web applications.
- Tip: I will then give you a tip, by default, application is uploaded at 5000 port, which you would require to change in many cases, I will show you how to change the port of the web application’s hosting service.
- Finally, I will head over to final words that I put at the end of every post that I write on any of the platform that I have to write about.
Installing or upgrading .NET Core
I wrote an article that covered how you can start using .NET Core on Linux environments, you can read it here. That article was written entirely, to give you a concept of the .NET Core architecture, and a few commands that you can use to do most of the stuff. The only difference between the older article and this section of the post is that this would just contain a later version of .NET Core to be installed on the system. Whereas in the previous one you had to install the older one.
Try the following,
sudo apt-get update && dist-upgrade
If that doesn’t work, or it doesn’t show the updates, head over to the main website for .NET Core, and install the latest version from there.
Creating a new web application
Previously, .NET Core only supported creating libraries or console applications. At the moment, it supports ASP.NET web application development too, it supports the templates for ASP.NET too, at the moment just a simple ASP.NET MVC oriented web application is created, and I don’t think there is any need for other templates like Web API, SignalR, single page applications etc. I believe that is complete at the moment.
To create a new web application, create the new project in .NET Core and pass the type parameter as a web application, which would guide .NET Core (dotnet) to create a new application with the template of web application.
Figure 2: Creation of a new .NET Core project using web template.
As you can see in the command above, we are passing a type (-t parameter) to the command to create a new web templated application. The content is as following,
Figure 3: ASP.NET Web application files and directories in .NET Core.
The project looks similar to what we have on Windows environment. Just a difference of one thing: It includes, web.config as well as project.json file. Remember that Microsoft is mostly moving back to MSBuild and of course a few of the hosting modules are based on IIS servers so that is why web.config file is available in the project. However, the project at the moment uses project.json file for project-level configuration and (as we have heard mostly during these days) these would be migrated to MSBuild way of managing the project and other related stuff.
Editing and updating the web application
Microsoft has been pushing the limits since a while, of course on Linux you already had a few of the best tools for development but Visual Studio Code is still a better tool. In my previous posts, I said that I don’t like it enough — I still don’t like it very much, it needs work! — but it is better than many tools and IDEs available for C# or .NET-related programming. Since in this post I said that I won’t be talking about anything third-party, so Visual Studio Code is the tool that I am going to suggest, support and use in this case.
You can install Visual Studio Code from their official website, note one thing, the Debian packages take a little longer for installation, so if you also don’t like to wait too much like me then I would recommend that you download the archive packages and install the IDE from them. There is no installation required at all, you just move the extracted files to a location where you want to store it. FInally, you create a symbolic link to your executable, which can be done like this,
sudo ls -s /home/username/Downloads/VSCode-linux-x64/code /usr/local/bin/code
This would create link and you can use Visual Studio Code IDE just by executing this “code” command anywhere in the directory (using the terminal), it would then load the directory itself as a project in the IDE which you can then use to update your application’s source code and other stuff that you want to.
Tip: Install the C# extension from market place for a greater experience.
Once this is done, head over to the directory where you create the project. Execute the following command,
This would trigger Visual Studio Code to load your directory as the project in the IDE. This is how my environment looks like,
Figure 4: Visual Studio Code showing the default ASP.NET directory as a project.
The rest is history — I mean the rest is the similar effect, and feeling that you can get on Windows environment. First of all, when you work this way and follow my lead you will get the following errors in the IDE window.
Figure 5: Error messages in Visual Studio Code.
We will fix them in a moment. But at first, understand that these are meant to act like this. If you have had ever programmed in .NET Core, you must have known that before anything else you need to restore the NuGet packages for your project before even building the project. Visual Studio Code uses the same IntelliSense and tries to tell you what is going wrong. In doing so, it requires the binaries which are not available so you are shown that last error message. Above two are optional, middle one is a bit optional-required.
Build and run the project
Until this point we have had created the project. But now we need to restore the dependencies for our project which are going to be used by the .NET Core to actually execute our code. By default a lock file is not generated, so we need to create a new file and after that we would be able to build the project.
Execute the following command,
After this, .NET Core would automatically generate the lock file and building process can be easily triggered.
Figure 6: Project.lock.json file created after restoring the project.
We can continue to building the project. I want you to pay attention to this point now. See what happens.
Figure 7: Build and run process of ASP.NET web application on .NET Core.
Now notice a few things in the above terminal window. First of all, notice that it keeps logging everything. Secondly, notice that it has a port “5000” appended. We didn’t train it to use that at all, and that also didn’t come from Program.cs file either (you can see that file!). But before I dig any deeper in explanation of how to change that, I want you to praise Kestrel — The web server of ASP.NET 5. Kestrel is the implementation of libuv async I/O library that helps hosting the ASP.NET applications in a cross-platform environment. The documentation for kestrel and the reference documentation is also available, and you can get started reading most of the documentation about Kestrel, on the namespace Microsoft.AspNetCore.Server.Kestrel at the ASP.NET Core reference documentation website.
This is the interesting part because ASP.NET Core can run even on a minimal HTTP listener that can act as a web server. Kestrel is a new web server, it isn’t a full feature web server but adapts as community needs updates. it supports HTTP/1 only as of now but would support other features in the coming days. But remember, pushing every single feature and module in one server would actually kill the major purpose of using the .NET Core itself. .NET Core isn’t developed to push everything on the stack, but instead it is developed to use only the modules and features that are required. Yes, if you want to add a feature you can update the code and build the service yourself. It is open sourced on GitHub.
Changing the port number of application
In many cases, you might want to change the port number where your server listens or you may also want to make this server the default server for all of your HTTP based communication on the network. In such cases, you must be having a special port number assigned (80-for default).
For that, head over to your Program.cs file, that is the main program file (main function of your project), and that is responsible for creating a hosting wrapper for your web application in ASP.NET Core environment. The current content for this object is,
Figure 8: Source code for the Program.cs file.
In that chain of “Use” functions, we just need to add one more function call to use a special URL. The function of “UseUrls(“”)” would allow us to update the URLs that are to be used for this web application. So I am just going to use that function here so that it would let us simply select which URL (and port) to use.
FIgure 9: URLs being managed.
Now, if you try to run the application you will run into the following problem in Linux-based system.
Figure 10: Unable to bind to the URL given, error message.
That is pretty much simple — it doesn’t have permission to do the trick. So what on Linux systems is done is that it simply is performed using the superuser credentials and account.
sudo dotnet run
It would prompt you for your password, enter your password and this time application would run on the localhost:80. In the cases where you have to upload the website to the servers, Azure App Services etc. In these cases, you are requires to have the application running under the server that acts as the default server, so in those cases you must handle the default TCP port for HTTP communication for the requests. Otherwise, you might require to work at the backends of NGINX or Apache servers etc. But that is a different story.
Figure 11: Web server running at port 80.
Now that our server is running, we can now go to a web browser to test it out. I am going to use Firefox, you can use any web browser (even a terminal-based).
Figure 12: ASP.NET Core web application being rendered in Firefox, running in Linux using Kestrel web server.
As you can see, the web application runs smoothly. Plus, it also logs any event that takes place. The terminal keeps a record of that, it can also allow you to actually transfer the output from main terminal’s output to a file stream to store everything. But that is a topic for a different post.
Figure 13: ASP.NET web application’s log in terminal window.
As requests come and responses are generated, this window will have more and more content.
I have wanted since a while, to write my own next web application for my own blog and stuff, in ASP.NET Core. At the moment, the framework is “almost” ready for production, but just not yet. Maybe in a couple of next builds it will be ready. There are many things that they need to look into. For example, the web server needs to be more agile — the features needs to be provided. That is not it, VIsual Studio Code must be fully integrated with ASP.NET Core tooling. At the moment it just allows us to edit the code, then we have to go back to the terminal to do the rest. It should provide us with the ability to do that.
To Microsoft’s team related to .NET Core: Why isn’t .NET Core being published on Linux? I am pretty much sure the framework is fully function, despite the bugs. But there are bugs in the main .NET framework too, there are some minor issues every here and there. My major concern here is to be able to do, “sudo apt-get install dotnet”. I can’t remember the longer version names.
To readers: If you are willing to use ASP.NET Core for your production applications, wait for a while. Althought ASP.NET Core is a better solution than many other solutions available. But my own recommendation is to stick to ASP.NET 4.6 as of now because that is more stable version as compared to this one.