PuTTY

PuTTY is a free, open-source terminal client for Windows that supports the SSH, Telnet, Rlogin and serial protocols. It is one of the most popular tools for managing servers remotely from the command line — the administrator logs into a Linux machine and runs commands as if sitting at its console. The program is lightweight, requires no installation and fits into a single executable.

How PuTTY works

On launch, PuTTY shows a configuration window where you enter the host address (an IP or domain name), the port (22 by default for SSH) and the connection type. The key aspects of working with it are:

• Sessions — named connection profiles you can save and load with a single click.
• Key authentication — instead of a password you can use an SSH key pair generated with PuTTYgen (the .ppk format).
• Pageant — an SSH agent that holds unlocked keys in memory so you don't re-enter a passphrase on every connection.
• Tunneling — port forwarding for secure access to services behind a firewall.

All traffic is encrypted, so passwords and data never travel across the network in cleartext — the fundamental advantage over the obsolete Telnet protocol.

PuTTY in practice

PuTTY is the default tool for administrators working on Windows:

1. Server management — configuring services, reviewing logs and restarting processes on a server or VPS.
2. Secure file transfer — the bundled psftp and pscp handle SFTP and SCP from the console.
3. Access to network devices — routers and switches are configured over the serial port.

Newer Windows versions also ship a built-in OpenSSH command-line client, yet PuTTY still wins on the convenience of managing many saved sessions and its clear graphical interface.