DNS
DNS is used to resolve domain names to get its matching IP. After getting the IP a GET request is send asking for root path, result in a 200 OK code when a file is found.
{% hint style="info" %} HTTP sents everything in cleartext while HTTPS sends all communications in encrypted formats. {% endhint %}
Requests and Responses
HTTP request is from client, containing details required from a server like resources, request data and headers. The server proceses and sends a HTTP response.
Request Headers
Headers are used to pass information between client and server, some are specific and some general.
| Header | Example |
|---|---|
| Date | Date: Wed, 12 May 2022 11:32:42 GMT |
| Connection | Connection: close |
| Content-Type | Content-Type: text/html |
| Content-Length | Content-Length: 385 |
| Content-Encoding | Content-Encoding: gzip |
| Host | Host: www.domain.com |
| User-Agent | User-Agent: curl/7.77.0 |
| Cookie | Cookie: PHPSESSID=b4e4fbd93540 |
Response Headers
| Header | Example |
|---|---|
| Server | Server: Apache/2.2.14 (Win32) |
| Set-Cookie | Set-Cookie: PHPSESSID=b4e4fbd93540 |
| Content-Security-Policy | Content-Security-Policy: script-src 'self' |
| Referrer-Policy | Referrer-Policy: origin |
HTTP Methods
Methods are used to tell server how to process requests we send and how to reply.
| Method | Description |
|---|---|
| GET | Requests resource. |
| POST | Sends data to server |
| HEAD | Requests headers |
| PUT | Creates new resource on server |
| DELETE | Deletes resource on server |
| OPTIONS | Show accpted methods |
| PATCH | Applies modifications to resource |
Reponse Codes
HTTP status codes tells client the status of a request. Most common are.
| Code | Description |
|---|---|
| 200 OK | Succesfull request |
| 302 Found | Redirect to another URL |
| 400 Bad Request | Returns malformed request |
| 403 Forbidden | No access to resource |
| 404 Not Found | Doesn't exist |
| 500 Interal Server Error | Server cannot process request. |