Control Multiple Computers with One Keyboard and Mouse
UPDATE November 30th, 2014: Synergy is no longer free. It’s still cheap, though.
Click here to Buy and Download Synergy.
From the website:
To accelerate the development of Synergy (improvements and features), we are now charging a small fee for the Synergy download. In the past, only 0.002% of users chose to donate, which was too little to support our team.
If you have questions about this, please check out the purchase FAQ below. Thanks for your understanding. We hope you decide to purchase Synergy and support the development of open source software. If you have any questions, please let us know.
Nick Bolton
Project Leader
The Synergy Project
It’s not such a bad thing, though. It’s only $4.95 for an outstanding piece of software that greatly boosts productivity when using multiple computers at the same seat. If you are new to Synergy: check it out. I promise you won’t be disappointed.
Years ago, I used a KVM Switch and skipped on the monitor switching to control multiple computers with one keyboard and mouse. Using a KVM switch was great and attributed to increased productivity and reduced desk clutter but it was clunky and sometimes the KVM switch would have to be reset. A good KVM switch isn’t cheap, either. But times have changed and technology has advanced.
A while back, I found software that allows me to share a single keyboard and mouse across multiple computers that are connected to the same network. Synergy allows me to drag my mouse from my primary workstation’s screen ONTO the screen of my laptop and click and type on my laptop using the keyboard and mouse that is connected to my desktop.
I used Synergy extensively for gaming. At the time I was playing Eve Online with 5 accounts at the same time. By using Synergy I was able to command a fleet of Internet Spaceships across 3 computers at lightning pace.
Synergy, previously known as Synergy+, is freemium software. The core software is free, but there is a “Premium” version available when you donate at least 1 USD. The premium version is something new and upcoming. Future premium versions will offer encryption (a feature that is currently offered for free) and the ability to drag and drop files. Synergy’s website does state that for every $10 donated the donor receives a single vote to put towards a feature request and the feature request with the most votes gets bumped ahead in the development timeline.
Synergy provides a lot more to the user than just sharing a keyboard and mouse. The user can configure monitor placement so if you wanted to stack monitors vertically or vertically and horizontally, the software can handle it. Additionally, Synergy supports clipboard sharing. While you cannot copy a file to the clipboard and paste it on another computer in your Synergy network, you can copy text, which is extremely handy when browsing the web on one computer for a URL and writing an article on the other that needs that URL.
Synergy also has a very active development atmosphere around it. Nifty features such as encryption, android device compatibility and the ability to drag and drop files between computers just as you would on a single computer are all being very actively developed.
Setting up Synergy
First of all, you’ll want your computer monitors for each computer relatively close – I have three monitors on my desktop (one is a laptop) that all sit next to each other. Additionally, Synergy works across your network so depending on the health of your network, you may notice a slight lag in response time on computers connected via Synergy, especially over a wireless network with heavy encryption enabled. If possible, be sure to connect all of the computers to an ethernet switch or router and avoid using a wireless connection. At my workstation I use a Netgear GS605 5-port copper gigabit switch which gives me outstanding performance and it didn’t frag my wallet. 
Once your hardware is in place, download the Synergy Software and install it on the computer that will have the keyboard and mouse attached that you want to use as the main controller. This computer will be known as the Server throughout this guide. As you can see in the image to the left, I have selected “Server (new setup)” during the setup process.
You’ll next be asked about encryption. Without encryption, Synergy will broadcast plain-text data about whatever you are typing, to include passwords. If your Computer A is the Synergy Server and Computer B is the Client and you use the keyboard on Computer A through Synergy to type in a password on Computer B, those keys are transmitted in plain text. Plain text is bad if someone is there listening to your network traffic through the use of a packet sniffer. If there is a risk of this on your network, you probably should select a form of encryption. If you are on a home network without a wireless network or you have a wireless network and security is set up and you are certain that there is no one in your vicinity that could be sniffing your wireless network traffic then you can probably disable encryption. Encryption will increase the response time of Synergy and because of that you should avoid encryption if you will be using a Synergy Client to play video games if a few milliseconds of response time are critical in whatever game you are playing. My workstation’s computers are all hard-wired to each other behind their own separate router with no other devices on their immediate network so the risk of someone sniffing my plain text data is practically zero so I’m not going to use encryption.
After configuring encryption, you will be taken to the main Synergy window. Your next step is to set up a Synergy Client and connect it to your Synergy Server.
Installing and Configuring Synergy Clients
Install Synergy the same way (unless you want to change some installation paths) until you get to the window shown the left. At this point select Client (add to setup) and click Next.
When asked about encryption, make sure you enter the same exact settings you entered for your server configuration. Once completed, click Next.
Connecting It All
Your next step is to get your client and your server connected and working together. If you enter the Server IP on the client Synergy window and click apply, you will see a bunch of entries in the log below “Connection was refused” or if you already started the Synergy Server you’ll see “failed to connect to server: server refused client with our name” and that is to be expected because you haven’t told the server which computers are connecting. The server doesn’t just allow any computer to connect, you have to configure it because the server needs to know where the client’s monitors are sitting relative to the server’s monitor(s).
To configure the server, click the “Configure Server” button on the main Synergy window on the Synergy Server and you’ll see the window to the left. (Click to Enlarge) Drag the computer monitor icon at the top right to wherever your computer is relative to your server’s display. In my case, my laptop sits to the left of my desktop so you can see that I’ve dragged the new display to the left of DESKTOP’s display.
Simply rename the new display to the hostname of the computer that you are connecting as a client. In my case my laptop’s hostname is LAPTOP. To do this, double-click on the computer display labelled Unnamed and rename it to the hostname of the synergy client. Click OK and you are done! My server configuration window looked like this when I was done. Once done with this step click Ok and then on the main Synergy window on the Synergy Server click Start.
In your log on the main Synergy window you should see this (image to the right), obviously with different names. I, however, did not and I had to click File then Save configuration as… and I actually had to save the file to a location that wouldn’t have spaces in the full path to the file, in my case I saved it to C:UsersJoesynergy.sgc. I then selected “Use existing configuration” and browsed for the file, then clicked Apply after which my laptop connected to my desktop and I was able to move the mouse freely about the two computers and type on either screen.
Advanced Settings for Advanced Geeks
Perhaps you want this to start up with your computers so you don’t have to go through the motions and start it all manually. It’s actually pretty easy to do. Synergy runs as a background service, the Synergy Window that we have been playing with is just a simple log viewer and configuration window.
Open the settings window by clicking Edit -> Settings. Check the box labelled Automatically start server/client and if you want to start the configuration/log viewer window you can select Start Synergy after logging in. You’ll have to configure these settings on each computer you are running Synergy on but it should be easy now that you can swing your mouse over to the other screens.
Everytime I mouse away from my game it minimizes or glitches!
That’s a pretty simple fix actually. Configure your game or games to run in Windowed Mode. A lot of games released today also feature a display mode called Fixed Window Mode which renders the game without the window border or window bar on top. You can configure the game to run at the same resolution as your desktop so it plays as if it was full screen and not windowed but is actually in a windowed mode – the best of both worlds. With Windowed Mode or Fixed Windowed mode enabled, your game won’t minimize or glitch while you play the game and multitask with Synergy. NOTE: Obviously not all games will have a reasonable Windowed Mode so you may have to resort to doing it old school and disabling Synergy on the Synergy Server when you play your games.
What will you be using Synergy for? Show us pictures of your setups in comments below!
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Love the article. Very informative. Must give a try.
One thing I didn’t mention in the article, this software works on Mac OS and you can mix and match windows and Mac computers within the same Synergy network.
I have also used Synergy for quite a while. One thing to be mindful of is that sometimes it doesn’t play well with games. I have run into some quirks where input won’t work correctly in-game, or the mouse loses focus from the game window even in full screen (especially if you have a second monitor on the gaming computer that doesn’t also display the game on it)