4.14.3 ‘Terminal-type string’Most servers you might connect to with PuTTY are designed to be connected to from lots of different types of terminal. In order to send the right control sequences to each one, the server will need to know what type of terminal it is dealing with. Therefore, each of the SSH, Telnet and Rlogin protocols allow a text string to be sent down the connection describing the terminal. On a Unix server, this selects an entry from the termcap or terminfo database that tells applications what control sequences to send to the terminal, and what character sequences to expect the keyboard to generate. PuTTY attempts to emulate the Unix xterm program, and by default it reflects this by sending xterm as a terminal-type string. If you find this is not doing what you want - perhaps the remote system reports ‘Unknown terminal type’ - you could try setting this to something different, such as vt220. If you're not sure whether a problem is due to the terminal type setting or not, you probably need to consult the manual for your application or your server.
The Telnet, Rlogin, and SSH protocols allow the client to specify terminal speeds to the server.
This parameter does not affect the actual speed of the connection, which is always ‘as fast as possible’; it is just a hint that is sometimes used by server software to modify its behaviour. For instance, if a slow speed is indicated, the server may switch to a less bandwidth-hungry display mode. The value is usually meaningless in a network environment, but PuTTY lets you configure it, in case you find the server is reacting badly to the default value.
The format is a pair of numbers separated by a comma, for instance, 38400,38400. The first number represents the output speed (from the server) in bits per second, and the second is the input speed (to the server). (Only the first is used in the Rlogin protocol.)
This option has no effect on Raw connections.
4.14.5 Setting environment variables on the server The Telnet protocol provides a means for the client to pass environment variables to the server. Many Telnet servers have stopped supporting this feature due to security flaws, but PuTTY still supports it for the benefit of any servers which have found other ways around the security problems than just disabling the whole mechanism.
Version 2 of the SSH protocol also provides a similar mechanism, which is easier to implement without security flaws. Newer SSH-2 servers are more likely to support it than older ones. This configuration data is not used in the SSH-1, rlogin or raw protocols.
To add an environment variable to the list transmitted down the connection, you enter the variable name in the ‘Variable’ box, enter its value in the ‘Value’ box, and press the ‘Add’ button. To remove one from the list, select it in the list box and press ‘Remove’.
The Proxy panel allows you to configure PuTTY to use various types of proxy in order to make its network connections. The settings in this panel affect the primary network connection forming your PuTTY session, and also any extra connections made as a result of SSH port forwarding (see section 3.5
). Note that unlike some software (such as web browsers), PuTTY does not attempt to automatically determine whether to use a proxy and (if so) which one to use for a given destination. If you need to use a proxy, it must always be explicitly configured.