add subject for localhost

subjects/localhost/README.md

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+## H-server
+
+The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems.
+HTTP is the foundation of data communication for the World Wide Web. Hypertext documents include hyperlinks to other resources that the user can easily access, for example, by a mouse click or tap on the screen in a web browser.
+
+### Instructions
+
+#### Server Part 
+
+The Client can be written in one of these languages [Go,C++,C...]
+
+```console
+$ ./localhost [CONFIG FILE]
+Server is Runing in http://[IP]:[PORT]
+```
+- Your server must not crash for any reason.
+- Any request to your server should never hang forever.
+- Your server can listen on multiple servers and ports at the same time without any conflict 
+- You must use the single process and no treads.
+- 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, default page error...)**
+- You must create error page at leat for [400,311,403,404,405,413]
+- You must execute CGI based on certain file extensions [`.php`,`.py`,...]
+- 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
+
+here is an example of an HTTP request with `GET` method
+
+```http
+
+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
+HTTP/1.1 404 Not Found
+Date: Thu, 19 Jul 2022 10:36:20 GMT
+Server: Hserver/1.1.0
+```
+> Learn about  [CGI](https://en.wikipedia.org/wiki/Common_Gateway_Interface)
+
+
+#### Configurations Part 
+
+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; //if it's "on," you should add the "upload_path"; otherwise, if it's "off," there is no need for "upload_status." 
+        
+        upload_path         /usr/share/nginx/upload; //depends on "upload_status"
+    }
+}
+```
+
+You have to base your server on this example but You have tested 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                     hello.com;
+    ...
+    ...
+    ...
+    location ...{
+
+    }
+    location ...{
+
+    }
+	location ...{
+
+    }
+}
+}
+```
+The Main Rules:
+- Choose the host(server_address) and a port or multiple ports of 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 In uploading.
+- 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/share, url /test/tmp/folder1/folder2 is /usr/share/test/tmp/folder1/folder2).
+  - Turn on or off the directory listing.
+  - Set a default file to answer if the request is a directory.
+
+to check the syntax of the config file you must run this : 
+
+```console
+$ ./localhost -t GoodConfigFile.conf
+Localhost : the configuration file GoodConfigFile.conf syntax is ok
+$ ./localhost -t WrongConfigFile.conf
+Localhost : the configuration file WrongConfigFile.conf syntax is not ok
+```
+
+If you’ve got a question about one behavior, you should compare your
+program behavior with NGINX’s.