Introduction to 127.0.0.1 Protocol- By: Musarrat Sheikh

Description : Internet Protocol addresses or IP addresses are numbers that can be seen behind URL's of sites on the internet. IP is the primary network layer for all applications found on the web. They are an extremely important set of numbers associated with the internet. The 127.0.0.1 is an Internet Protocol address that is also referred to as a local host. It forms the basic framework for loopback network connections processing. The basic meaning of loopback is to go back which is the basic function of this internet protocol address. Strictly speaking, this IP address is your machine's address. Whenever you use ftp, telnet or even try to access this IP address, you will be channeled back to your machine. The most important of this address are the first three digits i.e. 127. Any number combination involving the first three numbers will give you the same results.
A common joke among programmers is to have a novice to make connections to the above IP address. The 127.0.0.1 IP address carries with it some rather serious functions. It has some unique purposes and jobs. Network systems administrators or software developers use it to experiment with some unique or new set ups and applications. It is also used by experienced programmers who come up with software programs that are able to communicate with each other through the computer systems. It is also used in beta testing of several web applications like web browsers, activeX controls and Java applets. These operations start off with the sending of a message to the server. This message can only be sent in situations where this IP address is being used.
The result is usually a return to the site's host page in case the web browser relays the request. This local host IP address is also used in the interconnection of gaming servers to local hosts. The use of 127.0.0.1 internet protocol address ensures that the information flow as well as the entire process is efficient through appropriate streamlined operations. The local host cannot be used by nodes or network elements due to the simple reason that it is used a loopback. In case you desire to test some loopback functions of the local host, it is not a must that you be an experienced programmer.
All you have to do is to access your computer's operating system command prompt. Once there, type 'ping 127.0.0.1' at the c: part. You then proceed to hit the enter key which will give you a message like 'Reply from your local host...' Typing ping local host instead of the numbers will still generate the same results. If you are on telnet, you can still try it out. Let's assume that your computer's name is "Eric", this is what you are likely to get as the result.
# telnet local host...
Trying local host...
Connected to Eric...
Escape character is '^]'
IPv4 is the standard that is in use as concerns internet protocol addresses. There are a host of other reserved addresses that are also in use apart from 127.0.0.1. Such include 255.255.255 for broadcast, 10.0.0.0/8 for private networks, 192.88.99.0/24 for IPv6 to UPv4 relays among others.

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Author Resource : This article touched the basics of the topic. I have 2 more resources related to the above. They are 127.0.0.1 and 127.0.0.1. They are worth a read.