Helping people with computers... one answer at a time.

There are two approaches to sharing a display, keyboard, and mouse with multiple computers. I'll give a brief overview of both.

I have two computers but only one monitor, keyboard, & mouse. I would like to set up a network (I have a router), but do I need any other software or hardware so that I can see & work on each computer without plugging & unplugging cables into each?

Not only are computers cheap and their displays often somewhat expensive, but there's only so much room on people's desks and in homes. Setting something up so that you can access more than one computer from a single station makes a lot of sense.

Given that I have perhaps half a dozen computers that I deal with from time to time here at home, this kind of set-up is more than just sensible - it's a requirement.

I'll discuss one common option, why I don't use it (though you might), and what I do instead.

KVM Switches

Two computers connected to a single keyboard, display and mouse via a KVM switch

KVM stands for keyboard, video, and mouse; this is a hardware device where you connect a single keyboard, display, and mouse to one side and two or more computers to the other. The computer connections are made through the keyboard, mouse, and video connectors (a USB connector is often part of the mix), so you may end up with three cables from each computer to this box.

Aside from the cabling, it's conceptually very simple. You connect everything up and simply press a button to switch from one computer to another.

The only real expense is the KVM switch itself and any additional cables that might be required.

I don't have a specific recommendation but a quick search at your favorite online retailer will show you many, many options.

Now, I have to be honest. While it's been a few years since I've tried to use them, my track record with KVM switches is abysmal. The ones that I tried rarely worked well; occasionally, they didn't work at all.

I use a different approach completely.

Remote Desktop

Remote access to other computers via a network

My approach is to take advantage of the fact that all of my computers sit on the same local network.

I simply enable Remote Desktop Protocol (RDP) on all of the Windows machines.

Using Remote Desktop, I can open a window that "is" the remote computer and drive it pretty much as if I were sitting in front of it.

Example of Remote Desktop at work

In the screenshot above, you can see my desktop machine. The window in the center is the desktop of my laptop. I can then use my laptop simply by clicking on that window.

I have good news and bad news about this approach.

Good news:

  • If you have the Pro edition or better of Windows XP, Windows Vista, or Windows 7, you already have remote desktop software on your machine and that machine can be remote-desktopped to (computers 2 and 3 in the diagram above).

  • Any version of Windows (and, in fact, Mac and Linux as well) can run Remote Desktop client software (computer #1 in the diagram).

  • There's no limit on the number of computers that you can connect to at once. I occasionally find myself with half a dozen Remote Desktop windows open to my other computers.

  • After they've been set up, the computers that you connect to don't even need to have a keyboard, mouse, or display connected.

Bad news:

Once networked, running Remote Desktop is as simple as enabling Remote Desktop access on the computers that you want to connect to (typically, right-click My Computer, click Properties, click Remote), and running the Remote Desktop client on the machine that you want to physically use (typically, in All Programs, Accessories).

An alternative to Remote Desktop

As I mentioned, Remote Desktop is available only if you want to connect to Windows editions Pro or better. If you have Home edition, Remote Desktop isn't an option.

VNC, however, is.

VNC stands for Virtual Network Computing and is conceptually the same kind of technology as Remote Desktop with a couple of differences:

  • Remote Desktop "takes over" the computer - only one person can use it at a time. VNC technology allows the computer to be used from the computer itself at the same time as it's being accessed by one or more VNC clients. All users see the same session - meaning that keystrokes and mouse movements may collide, but all can see and interact on the same desktop.

  • VNC requires that you install a VNC server on the machines that you want to connect to and use a VNC client to connect.

There are several VNC packages available, often free for home use: RealVNC, TightVNC and UltraVNC are all popular candidates. (I happen to use RealVNC.)

Besides having several of the same pros and cons as Remote Desktop, VNC has one more: it's typically available on Macs and Linux by default.

Here's my desktop again; this time with a VNC window open to my Mac laptop:

VNC to Mac

Ultimately, there are two paths to go. My recommendation is to avoid additional hardware and take advantage of your existing network and free software to enable remote access of any of the machines that you have networked together.

Article C4825 - May 19, 2011 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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24 Comments
Sean
May 20, 2011 5:10 AM

thanks for all details!
I'm familiar with Teamviewer and a couple of VNC products.Cannot complain but sometimes VNC products are puzzling in work.
I would also recommend cost-effective alternatives. Techinline and Logmein free version are the easiest tools on the market as I think.
anyways it all depends on what you need to do exactly.

Mark
May 24, 2011 8:30 AM

I have used several KVM's from Trendnet and they perform flawlessly. If you choose I think a KVM is a good way to go. The new ones are smaller and all USB based rather than PS2 based.

Mike
May 24, 2011 8:40 AM

One draw back to RDP, VNC, etc is that occasionally a computer will have a problem (usually on a reboot) and hang before the OS gets started so software based solutions will not work. This is rare enough that you could just physically attach a monitor, etc. to the computer and solve the problem, but it does occur.

David
May 24, 2011 8:47 AM

I work out of my home office, and have two computers...one is my "work" computer, and one is my personal "home" computer. I do NOT have them on the same network, as they are kept independent of each other from a connectivity viewpoint, due to work security issues. So I use a KVM switch. Once in a while (about once every two weeks or so) it will "hang", and I need to re-boot both computers. But otherwise, works great, and makes it easy to only have one monitor, etc. and to be able to easily switch back and forth between work and personal systems.

Bay Geeks
May 24, 2011 8:50 AM

I'd like to suggest Synergy for the more tech savvy or adventerous. It's an open source project that allows you to install a small program on up to 12 computers and control them all with one mouse (similar to multiple monitors). It's a little tricky at first, but after reading the manual (last resort, I know!) it was a breeze.

Now I routinely work off of multiple computers and it's really made my life easier.


I don't work for them, just love using their product.


Hope this helps,


Alden

steven
May 24, 2011 9:00 AM

Does anyone here know why KVM switches do not always include Audio and a microphone support? Also, why are KVM switches 2,4,6 etc. At one time, I had three computers, until one was tossed.

Gabe Lawrence
May 24, 2011 9:31 AM

I've had fair to good experience with Belkin KVM's. They're cheap and they've worked, but like anything in technology, they have they're "bugs".

Also, Leo, just FYI, Windows XP SP2 & SP3 has a 10 connection limit. I've never tested it with RDP, but we have Samsung's "Link v3" software running on an XP box in our office and only 10 PC's can connect. With 11 PC's in the office, I'm able to confirm that the limit (System event 4226) does exist. I doubt this will be a problem in most home environments, but just thought I'd throw it out there.

Thanks for what you do. As an IT professional, I find myself learning at least one tidbit of wisdom from every email you send.

Betichung janvier
May 24, 2011 10:14 AM

woa i must confess it is awesome studing this.this is my first day to joine this side but with what i have learn today and with what i am going to gaining i know i must make a difference in my skoo.Ask leo this is the best research side i have ever come in contact i enjoy it.

Brad
May 24, 2011 10:15 AM

Mike said it, I agree..there are 'problems' with the RDP scenario.

If it WORKS for you, that's great. On your way to making it work, I would expect problems.

A couple examples...

Using RDP I can connect to an XP Pro machine using a Windows 7 Pro machine, but weird things happen. After the 'connection' is closed, all of the icons on the desktop of the XP machine have done their 'magical rearrangement' that Windows does sometimes, usually as a result of display resolution changes. And, no...the displays of the two machines are NOT set to the same resolution. I haven't bothered to set the resolutions the same to see if that resolves the icon issue. The two screens are not the same size, I won't USE the same resolution, so if setting them the same resolves anything, it won't matter in my situation.

Also, after the connection is closed, the mouse pointer disappears on the XP machine...but only IN an application window. I see it on the Windows desktop, but not in an Outlook window, for example.

Again..those are just a couple examples of issues I've experienced. There are more...those are just two.

RDP is not the 'It's just wonderful!' solution that a prospective user may think it to be is my point.

Oh..a hint that may be helpful: The 'host' machine must have a password set. If there is not a password, the machine attempting the access will complain of an 'incorrect' protocol, but it doesn't say anything about password requirement.

The 'host' machine (XP Pro in my case) DOES SAY a password is required during the RDP setup (in the 'remote' tab of 'System Properties'), but I missed that blurb the first time I tried it. The resulting 'protocol' complaint from the Windows 7 machine was puzzling (read: Irritating!) for a bit.

I suppose there are instances where it works exactly as expected...but I wouldn't count on it.

Definitely sounds like you'd had a lot of bad experiences with it, but I have to say that RDP has been nearly flawless for me over many years of using it.
Leo
24-May-2011

Tony Kightley
May 24, 2011 11:21 AM

Like you, Leo, I use more than one computer and each is set to specialise in one type of work - audio, photo, or e-mail/internet browsing. I have, always, used switches and, when they get tempremental, a good squirt of WD40 on the switch contacts works wonders! The mouse, keyboard and monitor use the normal KVM switches. Also, I use 4 (old) printers for different types of work and these are connected to the computers' parallel connectors with the usual cables. Two 4-way switches stand one on the other and common connectors of each are connected together with a short piece of flat cable which I wired to the central cores of the D-plugs, omitting the cases. This way, any of four computers can be connected to any of the four printers. The, only, snag with this system is remembering to switch to the appropriate printer before clicking on 'Print'! and I have used UltraVNC quite successfully on a local network, for computers not in the same room, or instance.

Derek
May 24, 2011 11:53 AM

I must say I've never had the problems that Brad mentions and I've been using remote desktop across five pc's for a long time.

Whilst, "officially", one cannot connect to an XP Home pc there are ways of fooling that pc's XP into thinking it's Pro and not violating your MS license. One doesn't even have to install extra XP software, just change some settings in the registry. None of my pc's have Pro and yet can all remote desktop via any permutation. Oh. MS updates and the software validation "thingy" have never complained.

Chris Bryant
May 24, 2011 4:56 PM

As always, a great email from Leo. Something simple, if only 2 computers are used. Buy a monitor with dual video in plugs and just use the monitor a/b button. I use two logitech wireless mice which have always worked flawlessly. Only drawback is I have to pull out the other keyboard, but this is easy and always works. I router the printers. I have tried the three major brand KVM's, and I too, had abysmal results. But not until I switched to the newer type connections and away from parallel's, etc. My old pc's/crt/Belkin auto KVM combo worked for years without a glitch. I upgraded everything a year ago, so maybe they have improved the KVM's since.

Win Bennett
May 24, 2011 6:57 PM

I have successfully used a kvm switch set up for years. All I have to do is press the insert key on the keyboard to access the other computer. The only thing I have to remember to do, when turning off one computer, is to make sure I get back to the other computer before the first turns off... otherwise I can't access it.

Simon Clarke
May 25, 2011 2:55 AM

I bought a Belkin fdk 102p kvm for very little ages ago. I can controll computers before the OS loads, which helps, sometimes! Key combination to switch between them is fast and reliable.

Marvin Burton
May 25, 2011 10:01 PM

Leo: I really enjoyed your article and became very anxious to try the VNC solution you discussed. Unfortunately, I find that I am at a loss as to how to proceed. I checked all three VNC packages that you mentioned, RealVNC, TightVNC, and UltraVNC. The free RealVNC does not cover Windows 7, so I skipped that one. TightVNC requires ver 2.x for Win 7 but the online documentation for installation specifically warns that it does not cover ver 2.0 or higher. I did install it but now I don't what to do next or how to configure it. Where am I supposed to find instructions if the software provider does not publish them? As for UtraVNC - I simply could not figure out what I needed to download or how to install it when I did. Again, a big lack of specifics and another quandary. It appears that these sites are for those who really know what they are doing; not for someone like me that has above average computer experience but is not a true geek. Nowhere could I find on any of these sites step-by-step installation instructions that I could follow with any confidence. Can you perhaps go a little deeper into how to setup either TightVNC or UltraVNC? I would certainly appreciate that and I feel confident that there are others who would like to give this approach a whirl, if only they knew how to do it. Thanks!!

Bette
May 26, 2011 6:45 AM

Marvin Burton's post addresses one of my concerns: will I, who knows next to nothing about computers, be able to figure out how to use a VNC program? Also, you didn't say anything about how to physically connect everything. I have three old computers I'd like to be able to connect to my monitor, keyboard, mouse, speakers, and external drive. I don't care if I can't access all of the computers at once. I just want to be able to use one set of peripherals with all of them. Is there an easier way? Thanks.

Gary Knop
May 26, 2011 12:15 PM

I am not sure if this will address Marvin or Bettes concerns , I use LogMeIn free. No cabling to do other than to my router, even less with a wireless card, though your response will suffer.

Marvin Burton
May 27, 2011 9:01 AM

Leo:

Here is an update to my previous comment. After some further research yesterday, I was able to get my VNC setup to control 2 computers running XP and 2 running Win 7. I am using TightVNC. The overall process was not that difficult and I highly recommend this solution to others. It really works great!!

The main breakthrough for me was to figure out the terminology that is used with VNC. The computers that are to be controlled are referred to as servers. A computer used to access and control a server is called a "client."

When downloading TightVNC, the installer will give the option of installing the SERVER and/or the VIEWER software. Install the SERVER software on every computer that is to be controlled (server), and the VIEWER software on every computer (client) that is to be used to control a server.

In configuring the server software, two passwords are setup: (1) the primary password, which allows access on the server software for future option changes, and, (2) the view-only password, which will need to be entered by the client computer before access is granted to the server computer.

Additionally, the IP address of all client computers that will be used to control a particular server will need to be added under "Access Control" when setting up each server.

For me, it was easiest to get this address by logging into my router and looking under the LAN settings for my client computer. I also set my router to reserve the same IP address for my client so that I would be assured that the same address would always be assigned to my client.

Most of the other server software settings were left to the default values, although I have been subsequently experimenting with these settings.

I found the setup for the Viewer software on the client machine to be very straight forward. I left most of the settings at the default values and placed an icon on my desktop.

To connect from the client to the server, open the viewer on the client computer. The viewer will ask for the name of the VNC server computer that is to be viewed and controlled. (Names can easily be obtained by looking at your network connections. The software will remember each name used for future use.) Once this is entered, press "Connect." Upon connection to the server computer a prompt will be given to enter the view-only password. Then BINGO!! You will now have control of the server computer.

Again, I highly recommend this solution. I am able to remotely log a grandchild into a computer from my computer and monitor what they are doing, if I feel it is necessary. I have also been able to do system maintenance on different computers from mine without having to jump around to each machine. For me, this has been an OUTSTANDING solution.

Thanks Leo, and keep those newsletters coming!!

Bette
May 28, 2011 4:36 AM

Cary Knop, thanks for trying to help, but I don't have a router (or even really understand what one does). Since money is an issue for me, I have to find the least expensive way for three computers to share one set of peripherals (if that's the right word).

suomynonA
June 2, 2011 7:31 AM

There is one small free program that gets the job done perfectly. I am not endorsed by them, and am saying this only out of my own free will:

A program called Synergy.

You install it onto both computers, set up the 'server' computer to have the keyboard and mouse, and the 'client' computer that will act as if its a 2nd monitor.

This is what i use all the time, since i have my laptop with all the harddrives, speakers, mouse, keyboard, programs, settings, and i recently added a 2nd desktop computer next to me to take some of the load off of this laptop. It connects through your home's router, and sends the movement from one to another.

The limitations are you must have at least one monitor for each computer, and auto-login at windows startup, and then have the program auto-start when the desktop loads. After you get that done the first time, it should be easy after that.

For me, my setup is:
[Desktop] [Laptop]-[TV Screen]. I have a total of 2 monitors, 2 computers, and some extra wires to connect the tv screen.

J. Page
September 12, 2011 8:49 AM

For several years I have operated several desktops from my recliner with laptop. Kavoom software KVM
http://www.kavoom.biz/ works perfectly. On rare occasions the tech help was needed........it was fast and sure. Around $14/per computer. Have never seen a bad review.

Adrian
January 2, 2012 11:52 PM

The downside to what you are suggesting is you cant use it for anything with high end graphics, for that a kvm switch would be better. for instance if you wanted to remote into a pc and run 2nd life you can't (i know i have tried tirelessly to do it). It is good however for viewing the web sharing stuff and other remote madness, also you could try logmein works in a similar fashion as RDC, but better. Try it out you might be pleasantly surprised. :)

Yeppers
February 24, 2012 12:21 PM

Leo, with regard to two computers that are connected by a KVM switch, if one of the computer is infected with a malware, does that KVM switch make it possible for the malware to be transmitted to the clean computer? Thanks…

I would not expect malware to travel over a KVM. I'd be more concerned about both machines being on the same network.
Leo
02-Mar-2012
Yeppers
May 6, 2012 3:36 PM

Leo, in the first diagram shown above (under the KVM Switches section), do you consider that setup to be a “network”? Thanks…

No. KVM switches connect only to the keyboard, video and mouse and do not add any kind of networking functionality. (There may be KVM-like products that work over a network, but they do not, themselves, add any networking.)
Leo
06-May-2012

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