Complete Telnet intrusion Manual

A major advantage of Internet systems is that it is as convenient to manipulate computers on the other end of the world as it is to use computers on the other side. This chapter describes how to use the telnet service system to connect to a remote computer.

We will discuss two main ways to use remote computers. First, you can register on any Internet host to obtain your account header. For a Unix computer, you must have a user ID and password. Once registered, you can use the host normally. Second, many Internet computers provide a public Telnet service. This system is valid for any user and generally does not require a password. Many resources in the appendix of this book are obtained in this way.

You will find that Telnet will make you forget the distance between yourself and the remote host. All you can feel is that when the Internet is used frequently, the computer's response speed is slightly slow. Of course, skilled users can easily access several different Internet hosts in turn.

Telnet Overview

As we have discussed earlier, Telnet provides a large number of services based on standard protocols. The service that connects you to a remote Internet host is called "Telnet ".

To use the telnet service, you must run a special telnet program on your computer. This program connects to your specified computer through the Internet. Once the connection is successful, Telnet works as an intermediary between you and another computer. Everything you input on the keyboard will be transmitted to another computer, And everything displayed on the other computer will be sent to your computer and displayed on the screen. As a result, your keyboard and screen seem to be directly connected to a remote computer.

In telnet, your computer is called a local computer, and the telnet program is connected to another computer called a remote computer ). These terms are used no matter how far the other computer is, whether in the same office or across the world. As described in Chapter 2, we often call an Internet computer a "host ". Therefore, using telnet, we can say that the function of the telnet program is to connect your local machine to a remote Internet host.

In addition, we usually use Telnet as a verb. For example, if you are visiting a friend's house outside China, you can say to him, "Can I use your computer? I want to telnet my computer to see if there is any email ."

The first method to run the telnet program

You should use the telnet program for remote connection. There are two methods to run the program. Here we will first describe one of the most commonly used methods. The next part will introduce another method.

Run the telnet program. First, enter the command name and the address of the remote machine you want to connect. For example, if you want to connect to a computer named fuzzball whose full address is fuzzball. UCSB. Edu, enter:

Telnet fuzzball.ucsb.edu

If you are connected to a computer on the local network, you can enter only the name of the machine instead of the full address. Example: Telnet fuzzball

As described in chapter 4, all Internet hosts have a formal IP address, which consists of a string of numbers separated by periods. For example, the IP address of a computer whose standard address is ucsd.edu is 128.54.16.1.

Some systems may have difficulties in processing certain standard addresses. If you encounter such problems when using the telnet program, you can try it with an IP address. For example, the following two commands can be connected to the same host for the same purpose.

Telnet ucsd.edu
Telnet 128.54.16.1

For more information about IP addresses and Internet addresses, see Chapter 4.

After running the telnet program, it starts to connect to the specified remote machine. When telnet is waiting for a response, the screen will display:

Trying...
Or similar information.

Once the connection is determined (if the host is far away, it may wait for a while), you will read this message: connected to fuzzball.ucsb.edu
Escape Character is '^]'

(We will explain this instruction in the next "coder)

If you cannot determine the connection through telnet, you will get information that the host cannot find. For example, assume that you want to connect to the remote host, "nipper.com", but you mistakenly enter:

Telnet nippet.com

You will see:

Nippet.com: Unknown hosttelnet>

In this case, you can specify another host name or stop the program.

Many factors may make Telnet unable to connect remotely. The three most common factors are misspelling of computer addresses.
Remote computers are currently unavailable.
The computer you specified is not on the Internet.

In addition, some problems may occur: for some reason, your local network may not be connected to some parts of the Internet. One reason is that some hosts are isolated for confidentiality. Another reason is that some hosts cannot be connected to other hosts at all.

For example, a friend from Ireland complained that he could not connect to a computer in Australia. In this case, Telnet displays information similar to the following:

Host is unreachable

In this case, check whether the Telnet command or address is entered correctly. You can also ask the system administrator to check whether the connection has some skills you do not know. Of course, if your location cannot be connected to a remote machine, you have to acknowledge the reality. (We had to say to the Irish friend: Many people have never been connected to Australian computers, but they still live a full and pleasant life .)

Once the telnet connection is confirmed, you can talk to the remote machine. At this time, many hosts will display some information, which is usually used to confirm the computer. Once the logon is accepted, you will see a standard prompt. For example, if you have been connected to a Unix remote machine, you will see:

Login:

Now you can log on in the regular mode. Enter your user ID and press Enter. You will see:

Password:

Enter your password and press Enter. (Note: The password you enter is not displayed on the screen. This is to prevent others from stealing your use right ).

We have pointed out that some remote machines can provide a public service, in which case you do not need to use a secret password when logging on. For example, in chapter 13th, we will discuss an Internet resource called Archie server. When you connect to the Archie server, an Archie user ID is used. Once this user ID is entered, the Archie program runs automatically. Some public hosts are even more convenient. As long as you use the Telnet command to connect, the remote program will be automatically executed, and you do not even need to enter the user ID and password.

After the remote machine is finished, you only need to "exit" in the conventional mode. The connection is disconnected and telnet stops running automatically.