Using telnet

Using telnet

Using telnet is not only very common, but also a simple to use terminal program. It is invoked by the telnet command on just about every operating system known to man that is running the TCP/IP protocol. TCP/IP is a protocol suite that allows telnet (and most of the rest of the utilities in this lesson) to function in the first place. TCP/IP is way beyond the scope of this book, but you should be familiar with what an IP address is if you are going to enter it here in the next example. As well, it should be noted that whenever you can, use ssh, which stands for secure shell. This protocol will provide you with encryption that can be used to secure a connection you would have normally made with the simple telnet program, which is not normally secure. Despite how insecure it is, there is still a large number of people out there that still use telnet all the time.

In telnet's primary use, it enables you to open a login session on a remote machine. To use the telnet command, issue the command as follows: telnet <remote machine>, where <remote machine> is either an IP address or a hostname. You will be prompted with a login and password prompt just as if you were sitting at the console of the remote machine. From here, follow the lessons learned in Lesson 1, "Getting Started," and you will be able to log in and use your Unix system remotely.

> telnet
> telnet pr1

In the last two examples, you can see that it is easy to telnet to a host. You need only to add the hostname or IP address after the telnet command, and the system will attempt to establish a connection (and telnet session) with the machine you specify. Make sure you master this skill; you will be doing this frequently if you use Unix often.

IP Addressing 101 IP addressing (in its simplest definition) is a string of four numbers separated by periods (such as used to represent a host (computer system) on the Internet. When a PC accesses the Internet through an ISP, it sometimes receives a temporary IP address and with that a name server assignment. This is how you surf the Internet something we will cover in more depth at the end of this lesson.

A hostname can only be used if you have the entry in your hosts file (remember that file from Lesson 8, "Text Editing," working with the vi editor) or are working with a name server that will allow you to specify the hostname. The server will get the IP address back to you.

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