PuTTY is a free software SSH, Telnet, rlogin, and raw TCP client. It was originally available only for Windows, but is now also available on various Unix platforms, with work-in-progress ports to Classic Mac OS and Mac OS X. Other people have contributed unofficial ports to other platforms, such as Symbian powered mobile phones. It is beta software written and maintained primarily by Simon Tatham, and is open source, licensed under the MIT License.