HTTP (HyperText Transfer Protocol) is a client-server protocol used for communication between a web browser and a web server. 

HTTP is a request/response protocol between clients and servers. When a client, such as a web browser, sends a request to a server, the server responds with requested web pages or other data. 

The protocol defines how messages are formatted and transmitted and what actions should be taken in response to various commands. 

It is the foundation of data communication for the World Wide Web. 

HTTP is an application layer protocol, meaning it is not concerned with the underlying transport layer (TCP/IP) but instead focuses on managing the transfer of data between the client and server. 

HTTP is an asynchronous protocol, meaning that a client and a server can communicate with each other independently and asynchronously.

HTTP is a stateless protocol, which means that the server does not keep track of previous requests from the same client. The server only processes the current request and does not remember previous requests. 

This makes it easier for servers to handle multiple requests from different clients simultaneously.

How Does HTTP Work?

HTTP is a set of rules and standards that define how data is transmitted over the internet. When a user requests a web page, their web browser sends an HTTP request to the server that hosts the web page. The server then responds with an HTTP response that includes the requested content.

Here’s how it works; we will discuss each in more detail later in this article:

• The Client Sends a Request: When a user types a URL into their browser or clicks on a link, they are sending an HTTP request to the server that hosts the website. The request typically includes a method (e.g., GET, POST), the URL of the webpage, and any additional data that the server may need to process the request.

• The Server Receives the Request: The server that hosts the website receives the request and processes it. This involves interpreting the method used, checking whether the requested URL exists and is accessible, and performing any necessary authentication or authorization checks.

• The Server Sends a Response: Once the server has processed the request, it sends an HTTP response back to the user’s web browser. This response typically includes a status code (e.g., 200 OK, 404 Not Found), headers (metadata about the response), and the requested content (e.g., HTML, CSS, JavaScript).

• The Client Receives the Response: The user’s web browser receives the response and processes it. This involves interpreting the status code to determine whether the request was successful or not, parsing the headers to extract any metadata, and rendering the content to display the webpage.

HTTP relies on a number of additional technologies to function properly. These include:

• TCP/IP: HTTP is built on top of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite, which is responsible for transmitting data over the internet.

• DNS: When a user types a URL into their browser, the browser uses the Domain Name System (DNS) to resolve the URL into an IP address that can be used to send the HTTP request.

• SSL/TLS: To ensure that HTTP requests and responses are transmitted securely, many websites use the Secure Sockets Layer/Transport Layer Security (SSL/TLS) protocol to encrypt the data in transit.

• Cookies: HTTP cookies are small pieces of data that can be used by web 

servers to track user activity and personalize the user experience.

What is HTTP Header?

HTTP headers are data sent along with the request or response between the client (your browser) and the server. They provide important information about the request or response, such as the type of data being sent, the encoding used, the language, and other important details.

HTTP headers can be divided into two types: request headers and response headers. Let’s discuss them in more detail.

What is in an HTTP request?

When you make a request to a web page, your web browser uses HTTP to send a request to the web server hosting the page, and the server uses HTTP to send a response back to your browser.

An HTTP request typically consists of several components, including:

HTTP Version Type

The version of HTTP being used to make the request, such as HTTP/1.1 or HTTP/2.

URL (Uniform Resource Locator)

The URL is the web address of the page or resource being requested. It specifies the protocol being used (HTTP or HTTPS), the domain name of the server hosting the web page, and the specific path to the resource being requested.

HTTP Method

The HTTP method is a verb that indicates the type of action being requested, such as GET, POST, PUT, DELETE, and so on. The most common HTTP method is GET, which is used to retrieve data from a server. Other methods, like POST and PUT, are used to send data to a server for processing.

HTTP Request Header

HTTP request headers are pieces of metadata that are sent along with an HTTP request from a client to a server. These headers provide information about the request being made, such as the type of request, the user agent making the request, and any additional data that may be relevant to the server processing the request.

Let’s explore some of the most common types of HTTP request headers in more detail:

• User-Agent: The User-Agent header provides information about the client making the request, such as the type of device, operating system, and web browser being used. Servers can use this header to optimize the response for the client, such as delivering a mobile-optimized version of a website to a mobile device.

• Accept: The Accept header specifies the type of data the client will accept in response to the request. This can include different file formats, such as HTML, JSON, or XML.

• Authorization: The Authorization header provides authentication information to the server, typically in the form of a username and password or an access token.

• Cache-Control: The Cache-Control header is used to specify caching instructions for the request and response. This can include directives to cache the response for a certain amount of time or not to cache the response at all.

• Content-Type: The Content-Type header specifies the type of data being sent in the request body, such as a form submission or an API call. This allows the server to properly process the data being sent in the request.

These are just a few examples of the many HTTP request headers that can be used to provide additional information and context to the server processing the request. By providing this additional information, clients can more effectively communicate with servers and optimize the response to meet their specific needs.

It’s important to note that while HTTP request headers can provide useful information, they can also be used to track user behavior and collect personal data. As a result, many web browsers and privacy-focused tools provide options to limit or disable the sending of certain HTTP request headers.

Here is an example of HTTP request header captured from the Google Chrome network tab for a request to a hypothetical website:

GET /api/data HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0
Accept: application/json
Authorization: Bearer 1234567890abcdef
Cache-Control: no-cache

In this example, the client is making a GET request to the /api/data resource on the example.com server. The User-Agent header indicates that the request is being made from a Windows machine using the Chrome web browser. The Accept header specifies that the client is willing to accept JSON data in response to the request.

The Authorization header provides authentication information to the server in the form of an access token. The Cache-Control header specifies that the client should not cache the response.

Optional HTTP Body

An HTTP request may include an optional body, which contains data that is being sent to the server. This is typically used for POST and PUT requests, which send data to the server for processing.

When all these components are put together, they form a complete HTTP request sent to the server hosting the requested resource. 

What is in an HTTP Response?

When a client (like a web browser) makes a request to a server using HTTP (Hypertext Transfer Protocol), the server responds with an HTTP response, which contains information about the requested resource. An HTTP response typically consists of three components:

HTTP Status Code

The HTTP status code is a three-digit code that indicates the outcome of the request. Status codes range from 100 to 599 and are grouped into classes, such as 2xx for successful requests, 3xx for redirections, 4xx for client errors, and 5xx for server errors. For example, a status code of 200 means the request was successful, while a status code of 404 means the requested resource was not found.

HTTP Response Header

HTTP response headers are pieces of metadata that are sent back by a server in response to an HTTP request made by a client. These headers provide information about the response being sent, such as the content type, cache directives, and any additional information that may be relevant to the client processing the response.

Let’s explore some of the most common types of HTTP response headers in more detail:

• Content-Type: The Content-Type header specifies the type of data being sent in the response body, such as HTML, JSON, or XML. This allows the client to properly process the data being sent in the response.

• Cache-Control: The Cache-Control header is used to specify caching instructions for the response. This can include directives to cache the response for a certain amount of time or to not cache the response at all.

• Server: The Server header provides information about the server software being used to process the request. This can include the server name and version, as well as any additional information that may be relevant to the client.

• Date: The Date header provides the date and time at which the server generated the response.

• Content-Encoding: The Content-Encoding header specifies the encoding applied to the response, such as gzip. This allows the client to properly decode the response data.

Here’s an example of HTTP response header captured from the Google Chrome network tab for a response to the same hypothetical website we used in the example of HTTP request header:

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: max-age=3600
Server: Apache/2.4.38 (Unix)
Date: Tue, 22 Feb 2023 16:43:45 GMT
Content-Encoding: gzip

In this example, the server is sending a 200 OK status code in response to the request. The Content-Type header indicates that the response is in JSON format. The Cache-Control header specifies that the client should cache the response for a maximum of one hour.

The Server header provides information about the server software being used to process the request. The Date header specifies the date and time at which the response was generated. The Content-Encoding header indicates that the response data is encoded using gzip compression.

Optional HTTP Body

An HTTP response may include an optional body containing the requested resource or other data being sent from the server to the client. This is typically used for responses to GET, POST, and other requests requiring data to be sent back to the client.

Together, these components form a complete HTTP response that is sent from the server to the client. The client can then use this information to process the response, display the requested resource, or take other appropriate action based on the response.

What is HTTP Port?

An HTTP port is like a gateway for communication between different devices over the internet. It is a numeric identifier that specifies a particular process or service on a computer accessible over the internet.

HTTP Port is simply the port used for transmitting HTTP data over the internet. The default port for HTTP is port number 80. When a browser requests a web page, it sends an HTTP request to the web server over port 80. The server then responds with an HTTP response containing the requested data sent over the same port.

For example, when you type http://www.example.com in your web browser, the browser sends an HTTP request to the web server of example.com on port 80, which is the default HTTP port. The server then responds with an HTTP response containing the requested web page’s HTML code.

In addition to port 80, other HTTP ports can be used, such as port 8080, which is often used as an alternative to port 80. This can be useful for developers testing web applications or for accessing web pages when port 80 is blocked by a firewall.

Why is HTTP considered Not Secure?

HTTP (Hypertext Transfer Protocol) is considered “not secure” because it sends data in plain text format, meaning anyone who intercepts the traffic can read the transmitted data. This can be a significant security risk, particularly when sensitive data such as login credentials, financial information, or personal data is being transmitted.

Let’s say you’re using an HTTP connection to log into your bank’s website. When you enter your username and password, the data is transmitted in plain text format, meaning anyone listening in on the network can intercept and read this data. This can allow an attacker to steal your login credentials and gain access to your bank account.

For example, if you were to look at the network traffic for an HTTP connection, you might see plain text data being transmitted like this:

Hi Imad, can you send me your password? My email is [email protected]

As you can see, this data is transmitted in plain text, which means that it could be intercepted and read by anyone who is listening in on the network.

In contrast, HTTPS (Hypertext Transfer Protocol Secure) uses encryption to protect the data being transmitted, making it much more secure. When you use an HTTPS connection to log into your bank’s website, your data is encrypted, so anyone who intercepts it will see only an unintelligible jumble of characters.

For example, if you were to look at the network traffic for an HTTPS connection, you might see encrypted data being transmitted like this:

AqrVXG4KPf+nKjJ3Lq4G2hf5v5jbYnH5e5S5PtKsbvh8yPWwfSwcLHJFYu+1KGZ2

As you can see, the encrypted data looks like a bunch of seemingly random characters, making it much more difficult for anyone to intercept and read the data. Only the sender and intended recipient, who have the necessary encryption keys, can understand the data.

To encourage the use of HTTPS, many web browsers now display warnings to users when they try to access a website that is not using HTTPS. 

This is to alert users that their data may not be secure and encourage them to be cautious when sharing sensitive information on the site.