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1c1af145 | 1 | \define{versionidintro} \versionid $Id$ |
2 | ||
3 | \C{intro} Introduction to PuTTY | |
4 | ||
5 | PuTTY is a free SSH, Telnet and Rlogin client for 32-bit Windows | |
6 | systems. | |
7 | ||
8 | \H{you-what} What are SSH, Telnet and Rlogin? | |
9 | ||
10 | If you already know what SSH, Telnet and Rlogin are, you can safely | |
11 | skip on to the next section. | |
12 | ||
13 | SSH, Telnet and Rlogin are three ways of doing the same thing: | |
14 | logging in to a multi-user computer from another computer, over a | |
15 | network. | |
16 | ||
17 | Multi-user operating systems, such as Unix and VMS, usually present | |
18 | a \i{command-line interface} to the user, much like the \q{\i{Command | |
19 | Prompt}} or \q{\i{MS-DOS Prompt}} in Windows. The system prints a | |
20 | prompt, and you type commands which the system will obey. | |
21 | ||
22 | Using this type of interface, there is no need for you to be sitting | |
23 | at the same machine you are typing commands to. The commands, and | |
24 | responses, can be sent over a network, so you can sit at one | |
25 | computer and give commands to another one, or even to more than one. | |
26 | ||
27 | SSH, Telnet and Rlogin are \i\e{network protocols} that allow you to | |
28 | do this. On the computer you sit at, you run a \i\e{client}, which | |
29 | makes a network connection to the other computer (the \i\e{server}). | |
30 | The network connection carries your keystrokes and commands from the | |
31 | client to the server, and carries the server's responses back to | |
32 | you. | |
33 | ||
34 | These protocols can also be used for other types of keyboard-based | |
35 | interactive session. In particular, there are a lot of bulletin | |
36 | boards, \i{talker systems} and \i{MUDs} (Multi-User Dungeons) which support | |
37 | access using Telnet. There are even a few that support SSH. | |
38 | ||
39 | You might want to use SSH, Telnet or Rlogin if: | |
40 | ||
41 | \b you have an account on a Unix or VMS system which you want to be | |
42 | able to access from somewhere else | |
43 | ||
44 | \b your Internet Service Provider provides you with a login account | |
45 | on a \i{web server}. (This might also be known as a \i\e{shell account}. | |
46 | A \e{shell} is the program that runs on the server and interprets | |
47 | your commands for you.) | |
48 | ||
49 | \b you want to use a \i{bulletin board system}, talker or MUD which can | |
50 | be accessed using Telnet. | |
51 | ||
52 | You probably do \e{not} want to use SSH, Telnet or Rlogin if: | |
53 | ||
54 | \b you only use Windows. Windows computers have their own | |
55 | ways of networking between themselves, and unless you are doing | |
56 | something fairly unusual, you will not need to use any of these | |
57 | remote login protocols. | |
58 | ||
59 | \H{which-one} How do SSH, Telnet and Rlogin differ? | |
60 | ||
61 | This list summarises some of the \i{differences between SSH, Telnet | |
62 | and Rlogin}. | |
63 | ||
64 | \b SSH (which stands for \q{\i{secure shell}}) is a recently designed, | |
65 | high-security protocol. It uses strong cryptography to protect your | |
66 | connection against eavesdropping, hijacking and other attacks. Telnet | |
67 | and Rlogin are both older protocols offering minimal security. | |
68 | ||
69 | \b SSH and Rlogin both allow you to \I{passwordless login}log in to the | |
70 | server without having to type a password. (Rlogin's method of doing this is | |
71 | insecure, and can allow an attacker to access your account on the | |
72 | server. SSH's method is much more secure, and typically breaking the | |
73 | security requires the attacker to have gained access to your actual | |
74 | client machine.) | |
75 | ||
76 | \b SSH allows you to connect to the server and automatically send a | |
77 | command, so that the server will run that command and then | |
78 | disconnect. So you can use it in automated processing. | |
79 | ||
80 | The Internet is a hostile environment and security is everybody's | |
81 | responsibility. If you are connecting across the open Internet, then | |
82 | we recommend you use SSH. If the server you want to connect to | |
83 | doesn't support SSH, it might be worth trying to persuade the | |
84 | administrator to install it. | |
85 | ||
86 | If your client and server are both behind the same (good) firewall, | |
87 | it is more likely to be safe to use Telnet or Rlogin, but we still | |
88 | recommend you use SSH. |