Putty

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PuTTY

PuTTY is a free and open-source terminal emulator, serial console, and network file transfer application. It is primarily used as a SSH and Telnet client, most notably on the Windows operating system.

Its main purpose is to provide users with a way to securely connect to and manage remote computers or servers that typically run Linux or Unix-like operating systems. By connecting via protocols like SSH, PuTTY gives you a command-line interface to interact with the remote machine as if you were sitting directly in front of it, but over a network.

Supported Protocols

PuTTY supports several network protocols for establishing connections:

  • SSH (Secure Shell): This is the most important protocol supported by PuTTY. SSH provides an encrypted connection, ensuring that data (like your login credentials and commands) transferred between your computer and the remote server is protected from eavesdropping. This is the secure standard for remote administration.
  • Telnet: An older, insecure protocol for remote command-line access. Data is sent in plain text, making it vulnerable to interception. It should generally be avoided for sensitive connections.
  • rlogin: Another older, insecure protocol for remote command-line access. Similar to Telnet, it sends data without encryption.
  • Raw socket connections: Allows connecting to arbitrary network ports for testing or specific applications.

Key Features

PuTTY includes several features useful for remote connectivity:

  • SSH authentication: Supports password-based authentication and more secure public-key authentication. It includes a separate tool, PuTTYgen, to generate SSH key pairs.
  • Port Forwarding (SSH Tunneling): Allows creating secure tunnels through the SSH connection to forward network traffic, which can be used to secure connections to other services.
  • File Transfer Clients: The PuTTY suite includes separate command-line utilities for secure file transfer: PSCP (for SCP) and PSFTP (for SFTP).
  • Customization: Users can customize the appearance of the terminal window, including fonts, colors, and window behavior.
  • Session Management: Allows saving connection details (hostname, port, protocol, settings) as sessions for quick access later.
  • Serial Port Access: Can connect to devices via a serial port, useful for managing networking equipment or embedded systems.

PuTTY Suite

PuTTY is not just one program but a collection of related executables:

  • putty.exe: The main terminal emulator client itself (for SSH, Telnet, rlogin, serial).
  • PuTTYgen.exe: A utility for generating SSH public/private key pairs.
  • PSCP.exe: A command-line client for transferring files securely using the SCP protocol.
  • PSFTP.exe: A command-line client for transferring files securely using the SFTP protocol.
  • Plink.exe: A command-line interface tool for running SSH, Telnet, and rlogin connections in scripts.
  • Pageant.exe: An SSH authentication agent that can hold your private keys in memory, allowing you to connect to multiple servers without re-entering your passphrase repeatedly.

Usage Scenarios

PuTTY is very widely used by administrators, developers, and users on Windows to:

  • Connect to Linux or Unix-like servers, including VPS and dedicated servers.
  • Manage network devices like routers and switches that support SSH or Telnet.
  • Access command-line environments provided by various appliances or systems.
  • Transfer files securely using PSCP or PSFTP.

Because SSH clients are typically built into Linux and macOS, PuTTY is most prominent in the Windows environment where it was historically one of the earliest and most popular free SSH clients available.

See Also

References

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