How Desktop Sharing Works

Let's say you're preparing a huge PowerPoint presentation for a big meeting on Friday. All of the PowerPoint files and PDFs and images that you want to use in your presentation are saved on the hard drive of your work computer. Thursday rolls around and you wake up with a nasty stomach virus. You don't feel well enough to go to the office, but you need to finish that presentation. Here's where remote login can help.

Until recently, virtual private networks (VPN) were the only way to remotely access work files from home. But VPN access isn't the same as accessing the hard drive of your work computer. VPN gives you access to the local area network (LAN) at your office. With VPN, you're only able to access your PowerPoint presentation files if you've saved them on the network, not just on your computer's hard drive.

Remote login, however, uses simple desktop sharing software to give you a "remote control" for accessing your computer -- and all of its software and hard drive files -- from any Internet-connected device anywhere in the world.

Remote login works exactly the same way as desktop sharing. In desktop sharing, there are two separate parties: the host computer and the remote user. To share a desktop, the host computer allows a remote user to view the contents of the host computer's desktop over the Internet. The host computer can also hand over keyboard and mouse controls to the remote user. With remote log-in, your home or work computer is the host and you (in this case) are the remote user.

Remote login requires three basic components:

[source: GoToMyPC]

For remote login to work, both the host computer and all remote users have to download and install the same desktop sharing software. Desktop sharing software typically includes two distinct programs:

[source: GoToMyPC]

Remote login will only work if the host computer is powered on, connected to the Internet and running the desktop sharing software. Each time you open and run the desktop sharing software on the host computer, the software starts a new session. Each session has a particular ID and/or password that's required to remotely log in to the host computer. Once the session has been established, most desktop sharing software quietly runs in the background of the host computer until a remote login request is made.­

To log in to the host computer from home (or while traveling), you'll need to run your version of the same desktop sharing software and enter in the correct session ID or password. Or some services allow you to log in through a Web site. Once you're logged in, both computers will communicate with each other over a secure desktop sharing network. Access to this network can be free or subscription-based, depending on the service. While connected, you'll have access to keyboard controls, mouse controls, all software and all files on the host machine.

For security purposes, all packets of information that are sent over the network are typically encrypted on each end with secure shell (SSH) or 128-bit advanced encryption standard (AES) encoding. For added security, no session IDs or passwords are stored on desktop sharing servers; they're automatically generated by the host machine.

Now let's look at real-time collaboration through desktop sharing.

One of the most common uses of desktop sharing is for real-time collaboration. Real-time collaboration is when two or more coworkers, classmates, colleagues or friends use desktop sharing software to simultaneously work on the same project, share files and work through problems as a team.

For example, let's say you're still stuck at home with that stomach flu and you need help coming up with the text for your PowerPoint presentation. Your coworker Nancy is a whiz with words, but she's at the office.­

Using desktop sharing, you and Nancy can log into a session and she can see the contents of your computer desktop. You can open up PowerPoint and show her the pages where you need help. You can even hand over control of your computer to Nancy so that she can type her text directly into the document, rather than just telling you over the phone or sending it to you in an e-mail.

A helpful feature of many desktop sharing programs is real-time annotating of documents. Whoever is in control of the host computer has access to the drawing and annotating tools, whether it's a remote user or the person sitting at the host computer. Common annotating tools are a highlighter, a freehand drawing tool and a pointer [source: GoToMeeting].

One of the most useful applications of real-time collaboration is for remote technical support [source: Real VNC]. You don't have to be a professional tech support operator to field frequent requests for computer help. If you're the member of the family with the most computer experience, you might get several calls a week from your grandma trying to access her e-mail, your dad trying to do video calls through Skype, or your sister trying to download music files.

Rather than trying to understand their computer questions over the phone (and deciphering their vague descriptions of their desktop), desktop sharing allows you to see exactly what they're doing, and in some cases do it yourself.

Professional technical support staffers have been using similar technology for the past few years to remotely diagnose hardware and software problems. Instead of walking the caller through the solution step by step ("Close all other applications. Restart your computer. Go to the Start menu and click 'Run'…"), tech support can use desktop sharing to jump into the driver's seat and fix the problem immediately.

On the next page, we'll talk about sharing presentations.

Another useful application of desktop sharing technology is presentation sharing. Like remote login and real-time collaboration, presentation sharing uses the same technology as basic desktop sharing. In presentation sharing, the presenter shares his or her desktop with a group of remote users to show a PowerPoint presentation or a Flash demonstration, to display photos or screen a video. Presentation sharing is inherently less collaborative and implies a one-to-many or few-to-many structure.

Other terms for presentation sharing are Web seminars or online presentations. In a Web seminar or online presentation, a presenter sends out an e-mail invitation to a group of attendees that includes a link and an access code. When the attendees click on the link and enter their access codes, they're logged into the virtual presentation.

In a Web seminar, there can only be one presenter at a time. The presenter can share his desktop, share presentations with programs like PowerPoint or Flash, or share other applications and software on the host computer. With Web seminar software, it's easy to switch presenters. Each presenter can then share his or her own desktop and files. But since Web seminars are one-to-many or few-to-many affairs, there usually isn't much changing of presenters.

Some real-world applications of presentation sharing and Web seminars are for salesmen who want to demonstrate a new software package to clients, for online continuing education classes and for online employee training.

As with other forms of desktop sharing, audio is usually separate from the Web presentation itself. The most common solution is to use teleconferencing. When the presenter sends out his invitation for the Web seminar, he can include a conference call dial-in number and an access code. Attendees would have to dial into the conference call, then log in to the Web seminar, or vice versa. Some subscription Web seminar services offer an option for bundling audio into the Web seminar using VoIP [source: Kolabora].

Now let's look at one of the coolest uses of desktop sharing: application sharing.

Like the other kinds of desktop sharing we've discussed in this article -- remote login, real-time collaboration and presentation sharing -- application sharing relies on the same basic screen-sharing technology. Application sharing uses the Internet to remotely view and control a particular software application on someone else's computer.

The greatest benefit of application sharing is that a remote user can run software that isn't installed on his computer, even software that isn't compatible with his operating system or that requires much more processing power than his computer can usually handle. This is because the remote user isn't actually running the software on his computer, he's just viewing and controlling the desktop (and therefore the software) of the host computer.

For example, an architect wants to present his designs for a large apartment building to his firm's partners. One of the partners is on vacation in the Bahamas and only has his old laptop computer with him. The architectural plans were created with a sophisticated computer aided design (CAD) program that requires a lot of processing power -- too much for the vacationing partner's little laptop. With application sharing, the architect can share his desktop with the partner and the partner can work with the CAD software remotely, never having to run the application on his laptop.

Application sharing is particularly useful for software salesmen and representatives. Traditionally, the only way for potential clients to test drive a software application was for the salesmen to travel to the client or for the client to attend a large trade show. But with application sharing, the salesmen can set up virtual sales appointments with the potential clients. Not only can he make his pitch with an engaging Web presentation, but he can hand over desktop controls to the client so the client can experience the software for himself.

For lots more information about desktop sharing and related topics, check out the links on the next page.