Web Server

• A web server is a software component that delivers static data like images, files, and text in response to client requests.
• When you enter the URL, the URLis actually of a Web Server
• Protocols: HTTP, FTP (files), SMTP (email)
• They deliver mostly static data
• Generally are not multi-threaded, use non-blocking I/O and callbacks
  • Are we talking about Nodejs?

Application Server

• An application server adds business logic to compute the web server’s response.
• The request to web server is transferred to the application server
• Protocols: web server protocols + protocols such as RPC, variants of CGI
• They deliver dynamic data such as personalized UIs, database results, processed HTML, dynamic reports etc.
• They are multithreaded

Notes

• The above are just common understanding since there is no exact definition describing the two
• The server can act as both Web Server as well as App Server for example:
  • Apache HTTP Server
  • Nodejs: Express, Hapi, Koa (Do we need to separate out static parts and dynamic parts)
• Django: recommends in production server:
  • serve static website parts with web server like Nginx or CDN. serving static parts with Django will introduce latency
  • dynamic part with app server like gunicorn
  • request —> Nginx (web server) —> Gunicorn (app server)
• ref:
  • https://aws.amazon.com/compare/the-difference-between-web-server-and-application-server
  • https://www.nginx.com/resources/glossary/application-server-vs-web-server/
  • https://developer.mozilla.org/en-US/docs/Learn/Server-side/Django/Deployment