PuTTY is a free implementation of an SSH and Telnet server, as well as a terminal emulator.
Information at https://www.chiark.greenend.org.uk/~sgtatham/putty/ with all credit to the original author, Simon Tatham.
We recommend downloading
putty.exe under Alternate Binary Files (32-bit or 64-bit) at https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html. This is a standalone version with no installation.
For a version of PuTTY that adds features that assist in troubleshooting and logging, please download ExtraPuTTY at http://www.extraputty.com/
ExtraPuTTY adds these useful features (and more):