public/subjects/localhost/README.md

Localhost

HTTP, HyperText Transfer Protocol, standard application-level protocol used for exchanging files on the World Wide Web.Each Web browsers are HTTP clients that send file requests to Web servers, which in turn handle the requests via an HTTP service.

Instructions

Server

The project can be written in one of these languages [Rust,Go,C++,C...]

• Your server must not crash for any reason.
• Any request to your server should never runing forever.
• Your server can listen on multiple servers and ports at the same time without any conflict.
• You must use only one process and no threads.
• You must use exec functions only in CGI part.
• Your server must be compatible with the last version of your chosen browser .
• You can use NGINX to compare headers and answer behaviors with your server.
• You must manage at least [GET, POST, DELETE] methods.
• You must handle customization errors (Binding error,wrong configue file...).
• You must create error page for at least for the following error codes [400,311,403,404,405,413].
• You must execute CGI based on certain file extensions such as [.php,.py,...] at least one.
• The CGI should run in the correct directory for relative path file access.
• You must use the enverement paramatre of CGI.
• Your server must receive a request from the browser and send a response using the HTTP header and body.
• Your server must call select function (or equivalent function) one time only.
• You must manage chunked and unchunked requests.
• You must set the right status for each response.

here is an example of an HTTP request with GET method:

GET /Welcome.html HTTP/1.1
User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)
Host: www.01talent.com
Accept-Language: en-us
Accept-Encoding: gzip, deflate
Connection: Keep-Alive

and here is an example of an HTTP response :

HTTP/1.1 404 Not Found
Date: Thu, 19 Jul 2022 10:36:20 GMT
Server: Hserver/1.1.0

Stress tests your server. It must stay available at all cost. use this command to test it siege -b [IP]:[PORT] the availability should be up to 95.99

Learn about CGI

Configurations File

This an example of a simple server configuration :

server {
    listen                          80;
    
    server_name                     localhost;
	
    root                            /usr/share/nginx/html;
    
    error_page          Mozilla 404        /usr/share/nginx/errors/404.html;
    
    client_body_size                10m; 
    location /
    {
        http_methods  GET  POST DELETE;
        
        index index.html
        
        upload_status on; 

        upload_path         /usr/share/nginx/upload; //depends on "upload_status"
    }
}

In the example above if the "upload_status" is "off", there is no need for "upload_path."

You have to base your server on this example bbut you must test also more complex configurations with multiple locations and ports and multiple servers such as:

{
server {
    listen                              80;
    server_address                      127.0.0.1;
    server_name                         localhost;
    ...
    ...
    ...
    location ...{

    }
    location ...{

    }
}
server {
    listen                              5000;
    listen                              5001;
    server_address                      192.182.2.1;
    server_name                         01edu.com;
    ...
    ...
    ...
    location ...{

    }
}
server {
    listen                          5001;
    listen                          5002;
    listen                          5003;
    server_address                  192.186.2.54;
    server_name                     01talent.com;
    ...
    ...
    ...
    location ...{

    }
    location ...{

    }
	location ...{

    }
}
}

The Main Rules :

• Choose the host(server_address) and a port or multiple ports for each server.
• The first server for a host:port will be the default if the "server_name" didn't mutch any other servers "server_name".
• Setup default error pages.
• Limit client body size for uploads.
• Setup routes with one or multiple of the following rules/configuration (routes won't be using regexp):
  • Define a list of accepted HTTP methods for the route.
  • Define an HTTP redirection.
  • Define a directory or a file from where the file should be searched (for example, if URL /test is rooted to /usr/Desktop, url /usr/Desktop/tmp/folder1/folder2).
  • Turn on or off the directory listing.
  • Set a default file to answer if the request is a directory.
  • No need to manage comments "(#)".

to check the syntax of the config file you must run this :

$ ./localhost -t GoodConfigFile.conf
Localhost : the configuration file GoodConfigFile.conf syntax is ok
$ ./localhost -t WrongConfigFile.conf
you miss server_addr in server 3

If your config file syntax is right :

$ ./localhost Myconfigfile.conf
Listening on [IP]:[PORT]
Listening on [IP]:[PORT2]

If you’ve got a question about one behavior, you should compare your program behavior with NGINX’s.

Bonus

• Add multiple CGI
• Create a php page and connect it with a mysql database.
• The "PHP" page should named mysql.php and should be in the root path.