The ssh client comes standard on Linux, Unix and Mac OS systems. The recommended ssh-based client for Windows is PuTTY. PuTTY can be downloaded via the PuTTY download page: www.chiark.greenend.org.uk/~sgtatham/putty/download.html.
Secure Shell (SSH) is a network protocol that allows data to be exchanged over a secure channel between two computers. Encryption provides confidentiality and integrity of data. SSH uses public-key cryptography to authenticate the remote computer and allow the remote computer to authenticate the user, if necessary.
SSH is typically used to log into a remote machine and execute commands, but it also supports tunneling, forwarding arbitrary TCP ports and X11 connections; it can transfer files using the associated SFTP or SCP protocols.
An SSH server, by default, listens on the standard TCP port 22.
An SSH client program is typically used for establishing connections to an SSHD daemon accepting remote connections. Both are commonly present on most modern operating systems, including Mac OS X, Linux, FreeBSD, Solaris and OpenVMS.