The SSH key exchange method that uses Diffie-Hellman group exchange was redesigned after its original release, to use a slightly more sophisticated setup message. Almost all SSH implementations switched over to the new version. (PuTTY was one of the last.) A few old servers still only support the old one. If this bug is detected, and the client and server negotiate Diffie-Hellman group exchange, then PuTTY will send the old message now known as SSH2_MSG_KEX_DH_GEX_REQUEST_OLD in place of the new SSH2_MSG_KEX_DH_GEX_REQUEST.
This is an SSH-2-specific bug.
The Serial panel allows you to configure options that only apply when PuTTY is connecting to a local serial line. 4.27.1 Selecting a serial line to connect to The ‘Serial line to connect to’ box allows you to choose which serial line you want PuTTY to talk to, if your computer has more than one serial port.
On Windows, the first serial line is called COM1, and if there is a second it is called COM2, and so on. This configuration setting is also visible on the Session panel, where it replaces the ‘Host Name’ box (see section 4.1.1
) if the connection type is set to ‘Serial’. 4.27.2 Selecting the speed of your serial line The ‘Speed’ box allows you to choose the speed (or ‘baud rate’) at which to talk to the serial line. Typical values might be 9600, 19200, 38400 or 57600. Which one you need will depend on the device at the other end of the serial cable; consult the manual for that device if you are in doubt.
This configuration setting is also visible on the Session panel, where it replaces the ‘Port’ box (see section 4.1.1
) if the connection type is set to ‘Serial’. 4.27.3 Selecting the number of data bits The ‘Data bits’ box allows you to choose how many data bits are transmitted in each byte sent or received through the serial line. Typical values are 7 or 8.
4.27.4 Selecting the number of stop bits The ‘Stop bits’ box allows you to choose how many stop bits are used in the serial line protocol. Typical values are 1, 1.5 or 2.
4.27.5 Selecting the serial parity checking scheme The ‘Parity’ box allows you to choose what type of parity checking is used on the serial line. The settings are:
•‘None’: no parity bit is sent at all.
•‘Odd’: an extra parity bit is sent alongside each byte, and arranged so that the total number of 1 bits is odd.
•‘Even’: an extra parity bit is sent alongside each byte, and arranged so that the total number of 1 bits is even.
•‘Mark’: an extra parity bit is sent alongside each byte, and always set to 1.
•‘Space’: an extra parity bit is sent alongside each byte, and always set to 0.
4.27.6 Selecting the serial flow control scheme