# Overview

Domain names and IP addresses are relayed through the **Domain Name System (DNS)**. The domain name connected to an IP address is given via a DNS pointer record, or PTR. 

Reverse DNS lookups make use of DNS PTR records. A **DNS lookup** happens when a user types in a domain name to access it in their browser, comparing the domain name to the IP address. In contrast, a reverse DNS lookup is a request that starts with an IP address and gets a domain name.

The domain name for the given IP address can be fetched using the `gethostbyaddr()` function of the `socket` module in python.

## The `gethostbyaddr()` function

The **`gethostbyaddr()` function** is used to retrieve the domain name for the given IP address.

> **Note:** Refer to [Socket programming in Python](https://www.educative.io/answers/socket-programming-in-python) to learn more about socket module in python.


## Syntax

```
socket.gethostbyaddr(ip_address)
```

## Parameter

- **`ip_address`**: This is the IP address for which the domain name has to be retrieved.

## Return value

The method returns a tuple, `(hostname, aliaslist and ipaddrlist)`.

- **`hostname`**: This is the domain name.
- **`aliaslist`**: This is a list of alternative host names for the same address.
- **`ipaddrlist`**: This is a list of IPv4/v6 addresses for the same interface on the same host.

## Example

import socket

def domain_name(ip_addr):
  dom_name = socket.gethostbyaddr(ip_addr)
  print("The domain name for " + ip_addr + " is", dom_name)

ip_addr = "8.8.8.8"
domain_name(ip_addr)

## Explanation

- Line 1: We import the `socket` module.
- Lines 3–5: We define a function called `domain_name`  that takes in an IP address and uses the `gethostbyaddr()` function to find the domain name function.
- Line 7: We define an IP address, such as `ip_addr`.
- Line 8: We invoke the `domain_name` function is with `ip_addr` as an argument.

How to find the domain name given an IP address

Reverse DNS lookups retrieve domain names using gethostbyaddr() in Python's socket module.

How to find the domain name given an IP address

Overview

The gethostbyaddr() function

Syntax

Parameter

Return value

Example

Explanation

The `gethostbyaddr()` function