What is Kestrel in ASP.NET Core ? How Kestrel Web Server Works ?

Raj Bhatt

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In the context of ASP.NET Core, Kestrel is a web server. It is a cross-platform, high-performance, and low-level web server for ASP.NET Core applications that is included as the default server in the .NET runtime. Kestrel is designed to handle high-performance, scalable web applications and can be used for both development and production environments. It can be run standalone or behind a reverse proxy server, such as IIS, Nginx, or Apache, to provide additional features such as SSL termination, load balancing, and caching.

Kestrel is a web server that runs directly on top of the operating system’s network stack and implements HTTP directly, without the use of additional software or libraries. When an ASP.NET Core application is started, Kestrel listens for incoming HTTP requests and processes them using the application’s middleware pipeline.

How Kestrel works :

The operating system receives an incoming HTTP request and sends it to Kestrel
Kestrel receives the request and performs initial parsing and processing, including URL routing and request header parsing.
Kestrel passes the request through the application’s middleware pipeline, which may include authorization, logging, and other custom logic.
The application generates a response and sends it back to Kestrel
Kestrel formats the response as an HTTP response and sends it back to the client.

Kestrel is designed to be fast and scalable, using asynchronous programming patterns and taking advantage of the low-level capabilities of the underlying operating system. It can handle high-performance workloads and can be configured to run behind a reverse proxy server for added security and scalability.

Advantages of using Kestrel

Cross-platform: Kestrel is a cross-platform web server that runs on Windows, macOS, and Linux. This allows developers to write and deploy their applications on any operating system.

High performance: Kestrel is designed for high-performance, scalable web applications. It is implemented in a low-level, efficient manner and uses asynchronous programming patterns to handle high volumes of requests.

Lightweight: Kestrel is a lightweight and simple web server, making it easy to integrate with other components and systems. This allows for fast and flexible deployment of ASP.NET Core applications.

Flexible deployment: Kestrel can be run standalone or behind a reverse proxy server, such as IIS, Nginx, or Apache. This gives developers the flexibility to choose the best deployment configuration for their application, depending on their requirements.

Security: Kestrel supports secure connections using SSL/TLS, and it can be configured to run behind a reverse proxy server to provide additional security features, such as SSL termination, load balancing, and caching.

Kestrel is a cross-platform, open-source web server that is included with ASP.NET Core. It is the default web server for ASP.NET Core and provides a high-performance, scalable solution for hosting web applications.

Kestrel is a lightweight server that is designed to be simple, fast, and efficient. It uses asynchronous I/O to handle incoming requests and can process thousands of requests concurrently. It is also optimized for serving static files, which can improve the performance of web applications.

Tuhin Paul

Kestrel is a cross-platform web server that is used as the default and built-in web server in ASP.NET Core. It is designed to be fast, lightweight, and scalable, making it ideal for hosting web applications and services on the server.Kestrel works by implementing the HTTP server directly on top of the operating system's sockets. This allows it to handle requests and serve responses with low overhead, as it bypasses the traditional architecture of using a web server (such as IIS) as a reverse proxy for processing incoming requests.When a request is received by Kestrel, it first parses the incoming HTTP request and then routes it to the appropriate endpoint in the application. The application logic then generates a response, which Kestrel then sends back to the client over the network. Kestrel also handles security concerns such as SSL encryption, request and response caching, and response compression, making it a full-fledged web server.In summary, Kestrel is a fast, efficient, and secure web server that is optimized for hosting ASP.NET Core applications, and it is an integral part of the ASP.NET Core ecosystem.

Manoj Kumar Duraisamy