What Is 127.0.0.1 Localhost?

How Does a 127.0.0.1 Loopback Work?

When we request the http:/localhost in any web browser, it is not forwarded as a typical TCP/IP request. Here, the host computer's operating system manages the request. The connection is made on a local network and connects the hosting computer. This is the reason it is also called a Loopback address. The request is looped back and connected to the machine making the request.

The below Diagram shows the working of the Loopback address as explained above.

The following message is generated if we have not hosted a server on the machine when we connect through http://localhost.

This happens as the localhost is not expecting any connections. As soon as we run a server on the machine, the localhost starts listening to the requests, and the above message is removed.

The Loopback message is also associated with a port number and IP address. These port numbers help to divide the server load and run multiple servers.

The TCP/IP recognizes the 127.0.0.1 localhost as a special IP address. The message is re-routed for any request corresponding to the IP address 127.0.0.1. The following ping command gives the visualization of the localhost and its working.

Here, we see that making a ping request to 127.0.0.1 shows a successful connection is established with the same machine. The figure also shows the round trip time and the average time for connection establishment.

The TCP/IP also checks for the requests arriving at the routers. The network gateways discard the connection if the loopback IP address is found. This is used as an application for blocking malicious websites (Discussed Later in the article).

What is 127.0.0.1 Localhost Used For?

The Localhost provides a wide range of applications to developers. Developers use it extensively to test web applications. It is also used for network testing by the network administrators. It is also used for blocking malicious websites and preventing the computer from malfunctioning.

Now, we will discuss some of its Uses in detail.

Blocking Malicious Websites

The local host is used to block malicious websites and eavesdropping attacks. The Localhost is used to host files and servers in a computer.  The hosted files have IP addresses associated with them. Similar to the working of a Domain Name Server where a domain name is looked for in a global DNS. The host file has the IP address which can be used to access the file.

Usually, the host file consists of just two entries. Below is the host file of a user, which is available as \system32\drivers\etc\hosts in Windows and /etc/hosts in Unix or MacOS.           

This host file is used to block some malicious websites. This is done by entering the domain name of the target website and assigning it 127.0.0.1 localhost. Doing this prevents the system from looking for the site over the Internet. It returns it searches for the 127.0.0.1 localhost. If no server is hosted on the computer, it responds that it cannot connect to the wanted site. If any server is hosted, the user is directed to the same.

Hosting Web Application Locally

The developer uses the 127.0.0.1 localhost for hosting the web applications. Local hosting helps developers to debug the application. It provides an overall environment for testing and learning. It can help developers to experiment with different technologies and make robust web applications.

A wide variety of platforms available can help with the same. These platforms provide the necessary components for web development on the 127.0.0.1 localhost. Some popularly used tech stacks are LAMP, WAMP, MAMP, MERN, and others.

Testing of Web Applications

A significant part of web development is the ensure the application works as supposed. The 127.0.0.1 localhost is used for testing web applications. The localhost can simulate the working of a virtual network. This can be used for testing. 

Moreover, the 127.0.0.1 localhost has the advantage of its speed. The request sent over the Internet usually takes more than 100 milliseconds. However, using the ping commands for network testing takes only a millisecond. It can save a lot of development time. 

In the working of the 127.0.0.1, we saw an image of ping. It can be used to check the implementation of the protocol is correct or not. 

We can type the following command in the Unix/macOS or Windows terminal:

ping localhost
ping 127.0.0.1

There are various software available for setting up your test servers. Some software even provides the facility of delivering localhost capabilities. XAMPP is one of the most popularly used software which can be used as localhost.

What is the Difference Between 0.0.0.0 and 127.0.0.1?

Sometimes you'll come across another IP address called 0.0.0.0, which does the same job as 127.0.0.1. However, when you compare them, you'll find they perform two completely different tasks.

127.0.0.1 signals the TCP/IP of your computer that it don not want to connect to the Internet. It states a connection to a server hosted on the same computer. As such, you'll typically enter it when telling the software to connect to a server via a web browser or a game.

0.0.0.0, on the other hand, is more of a wildcard than a specific location. When you use 0.0.0.0, you tell the software to allow connections from every local IP address possible instead of just 127.0.0.1.

Frequently Asked Questions

What is an IP address?

An IP address is a unique address assigned to any machine that is used to identify the machine. It helps to facilitate communication in a network by assigning a unique address to the machines that are requesting or responding.

What is the use of 127.0 0.1 localhost? 

127.0.0.1 localhost is a loopback address which is used to access the local host referring to the current device. It allows testing web applications locally and network services without a live internet connection. 

What is the meaning of 127.0 0.1 8080?

127.0.0.1 8080 represents the IP address and port number for a local server. It allows accessing applications running on port 8080 on the same device. It is useful for testing web services and running applications on a dedicated port.

Can we change the IP address 127.0.0.1?

Yes, it is possible to change the IP address 127.0.0.1. We have to modify the host file present on the system. We can assign a different hostname to 127.0.0.1 in these host files for local testing.

Conclusion

This article taught us about the 127.0.0.1 IP address or the localhost. We learned about the working of 127.0.0.1 localhost. We also discussed the applications of the localhost. We saw how it can block malicious websites and test web applications.

To learn more about 127.0.0.1 Localhost and other related topics, you can check out our other blogs.

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• Flask Introduction
   

Check out some amazing Guided Paths on topics such as Data Structure and Algorithms, Competitive Programming, Basics of C, Basics of Java, etc., only on Coding Ninjas Studio. 

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