Remote access services: Telnet, SSH, rdesktop, VNC

Secure Shell, commonly known as SSH, and Telnet are two network protocols that have been used widely at one point in time or another. They are both used to connect to remote servers in order to facilitate some sort of communications. The primary difference, which also led to one superseding the other, is in security. SSH offers security mechanisms that protect the users against anyone with malicious intent while Telnet has no security measures whatsoever. Telnet was designed to work within a private network and not across a public network where threats can appear. The security issues of Telnet forced many people to use SSH in order to protect themselves. It didn’t take a long time before SSH replaced Telnet in a great majority of its uses. Telnet did not fade away though as it is still used in some areas, mostly in testing and debugging.

rdesktop is an implementation of a client software for Microsoft's proprietary Remote Desktop Protocol (RDP). Rdesktop is free and open-source software, subject to the requirements of the GNU General Public License (GPL), and is available for Linux and BSD as well as for Microsoft Windows. Rdesktop is commonly used on desktop ReactOS and Linux installations to connect to Microsoft Windows running Remote Desktop Services. There are many GUI clients, which are graphical front-ends to rdesktop.

In computing, Virtual Network Computing (VNC) is a graphical desktop-sharing system that uses the Remote Frame Buffer protocol (RFB) to remotely control another computer. It transmits the keyboard and mouse events from one computer to another, relaying the graphical-screen updates back in the other direction, over a network. VNC is platform-independent – there are clients and servers for many GUI-based operating systems and for Java. Multiple clients may connect to a VNC server at the same time. Popular uses for this technology include remote technical support and accessing files on one's work computer from one's home computer, or vice versa. There are a number of variants of VNC, which offer their own particular functionality; e.g., some optimized for Microsoft Windows, or offering file transfer (not part of VNC proper), etc. Many are compatible (without their added features) with VNC proper in the sense that a viewer of one flavour can connect with a server of another; others are based on VNC code but not compatible with standard VNC.