| 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. |