Desktop sharing

Desktop sharing is a common name for technologies and products that allow remote access and remote collaboration on a person's computer desktop through a graphical Terminal emulator.

The most common two scenarios for desktop sharing are:

• Remote log-in
• Real-time collaboration
  
• Desktop sharing uses simple software to share files, presentations and applications over the Internet -- in real time -- with colleagues and clients around the world. Desktop sharing is a central component of Web seminars and Web conferences, enhancing our ability to interact and collaborate over long distances.
• Desktop sharing has many applications.
• Remote login allows workers to access their work computers from any Internet-enabled device, including home computers, laptops and even PDAs.
• Desktop sharing allows for interactive, real-time collaboration between global co-workers.
• Presentation sharing turns dry teleconferences into engaging on line presentations.
• Application sharing lets you test drive software without buying, downloading or installing anything.
• Desktop sharing software works by sending packets of information from a host computer to a remote computer describing what's on the host computer's screen at any given time. The encrypted data travels over the Internet. Some data arrives as image files (JPEGs and GIFs), while others arrive as individual pixels assigned to a particular X and Y coordinate. Desktop sharing software is smart enough to only send information updates on the sections of the screen that have changed and to compress the data significantly, minimizing the amount of necessary bandwidth [source: Go To My PC].­
• In this How Stuff Works article, we'll explain the technology, applications and features of desktop sharing, including remote log-in, real-time collaboration, presentation sharing and application sharing.
  

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Terminology:

• Listening mode: where a server connects to a viewer. The server site does not have to configure its firewall/NAT to allow access on port 5900 (or 5800); the onus is on the viewer, which is useful if the server site has no computer expertise, while the viewer user would be expected to be more knowledgeable.
• Audio Support: the remote control software transfers audio signals across the network and plays the audio through the speakers attached to the local computer. For example, music playback software normally sends audio signals to the locally attached speakers, via some sound controller hardware. If the remote control software package supports audio transfer, the playback software can run on the remote computer, while the music can be heard from the local computer, as though the software were running locally.
• Built-in Encryption: the software has at least one method of encrypting the data between the local and remote computers, and the encryption mechanism is built into the remote control software.
• File Transfer: the software allows the user to transfer files between the local and remote computers, from within the client software's user interface.
• Seamless Window: the software allows an application to be run on the server, and just the application window to be shown on the clients desktop. Normally the remote user interface chrome is also removed, giving the impression that the application is running on the client machines.
• Remote Assistance: remote and local users are able to view the same screen at the same time, so remote user can assist a local user.
  
• Access Permission Request: local user should approve a remote access session start.
• NAT Pass through: the ability to connect to the server behind a NAT without configuring the router's port forwarding rules. It gives an advantage when you can not configure router (for example it is on Internet service provider's side), but is a serious security risk (unless the traffic is end-to-end encrypted), because all the traffic should pass through some proxy server which in most cases is owned by remote access application's writers.