Web Server & Web Application Server

Web Server

Web server is a program that provides static contents like HTML documents by receiving HTTP request from the web browser (client).

Static contents mean that no matter what parameters or users will be, the response always includes the same contents.

Web Server's Functionalities

Receives HTTP request from the client

For static contents, the server can provides static contents (html, jpeg, css, etc.)

For dynamic contents, the server delivers dynamic contents request to Web Application Server (WAS), and pass results from the WAS.

Web Application Server (WAS)

Web application server is a program that is implemented for providing dynamic contents which require various logic processes or DB queries.

Dynamic contents can be varied from the input parameters or users

WAS can

directly receive HTTP request from the client

provide static contents (html, jpeg, css, etc.)

provide dynamic contents by processing various logics and DB query

Why we need WS for WAS?

We may need WS because we can separate the roles between WS (for static contents) and WAS (for dynamic contents).

If we use multiple WAS, then WS can be a load balancer to distribute the request calls from the client.

WS can regularly check the WAS health (check if response comes correctly)

We can use reverse proxy from WS to secure the data from the WAS.

Common Web Server Software

Apache HTTP server

Nginx

Sun Java System Web Server

...