User FAQ

Paul Chvostek edited this page Dec 22, 2016 · 23 revisions

Table of Contents

Frequently Asked Questions

This page is useful for solving common problems when using Synergy. For a guide on how to setup Synergy, please see the User Guide. This FAQ is based on the original FAQ written for version 1.1 and may need updating.


Can the server and client be using different operating systems?

Yes. The Synergy network protocol is platform neutral so Synergy doesn't care what operating systems are running on the server and clients. This also applies between 32-bit and 64-bit OSes.

Can Synergy do drag and drop of files between computers?

Yes! This is supported on Windows Vista and newer, and Mac OS X 10.7 and newer. You must drag a single file icon to the edge of the screen in the direction of the client or server, and the file will be copied to the desktop of the other computer a few seconds later. This has some limitations depending on version of SSL and whether SSL is running, partially fixed for 1.7.3 and to be much improved for 1.7.4.

Can Synergy share the display in addition to the mouse and keyboard?

No. Synergy is a KBM (KeyBoard, Mouse) solution not a KVM (Keyboard, Video, Mouse) solution. However, future versions will probably support KVM. Hopefully, this will make Synergy suitable for managing large numbers of headless servers.

Does Synergy do drag and drop of windows?

No. Synergy does not currently do anything with video or visual elements. This is a frequently requested feature so we are always keeping an eye out for ways to accomplish this.

What's the difference between Synergy and x2x, x2vnc, etc?

Unlike x2x, synergy supports any number of computers and it doesn't require X on Microsoft Windows platforms. It also has more advanced clipboard support and synchronizes screensavers. x2vnc is also limited to two computers, requires the separate VNC package, and is really only appropriate for using an X system to control a non-X system. However, the right tool for the job is whatever tool works best for you.

What security/encryption does synergy provide?

Synergy uses SSL encryption (available to Pro edition users).

Strong encryption and authentication is also available through SSH (secure shell). Run the SSH daemon (i.e. server) on the same computer that you run the Synergy server. It requires no special configuration to support Synergy. On each Synergy client system, run SSH with port forwarding:

 ssh -f -N -L 24800:server-hostname:24800 server-hostname

...where server-hostname is the name of the SSH/Synergy server. Once SSH authenticates itself, start the Synergy client normally, except use localhost or as the server's address. SSH will then encrypt all communication on behalf of (or in addition to) Synergy. Authentication is handled by the SSH authentication.

A free implementation of SSH for Linux and many Unix systems is OpenSSH. For Windows there's a port of OpenSSH using Cygwin.

What is Bonjour and why do I care?

Bonjour is one application of the ZeroConf protocol, which was originally designed for things like printers and scanners to be automatically found on a network when a new computer connects. In the old days, you would have to dig into the printer's settings or print a label on the front of the printer to find its IP address and add it to your setup manually. This protocol was developed to make this process easier. It was also designed to be used with anything which needed to have a client find a server, which is the case with Synergy. We use ZeroConf (Bonjour) to allow Synergy Clients to automatically find Synergy Servers. It's not perfect yet, sometimes it still picks the wrong IP to connect to, in which case you will need to uncheck “auto config” and enter in the correct IP manually. We hope to improve this feature in future versions until it is one of those “can't live without” sort of things.

Why isn't Synergy ported to platform XYZ?

Probably because the developers don't have access to platform XYZ and/or are unfamiliar with development on XYZ. Also, Synergy has inherently non-portable aspects so there's a not-insignificant effort involved in porting.


Do all computers need to be on the same network?

Can the client ping the server? If so, then Synergy should work. Can the client reach the server via SSH? If so, then Synergy should work using methods related to SSH encryption, described above. If the client can't connect to the server either directly or through a tunnel, then you'll be unable to use Synergy. You may be able to use VPN to connect the client to the same network as the server (if you're in a corporate environment, ask your system administrator).

What should I call my screens in the configuration?

The short answer is that you should use the name Synergy automatically detects whenever possible. In the GUI, this appears under the Client section, labeled Screen Name.

You can use any unique name in the configuration file for each screen but it's easiest to use the hostname of the computer. That's the computer name not including the domain. For example, a computer with the fully qualified domain name has the hostname xyz. There should also be an alias for xyz to If you don't use the computer's hostname, you have to tell Synergy the name of the screen using a command line option, or the startup dialog on Windows.

Some systems are configured to report the fully qualified domain name as the hostname. For those systems it will be easier to use the FQDN as the screen name. Also note that a Mac OS X system named xyz may report its hostname as xyz.local. If that's the case for you then use xyz.local as the screen name.

How do I stop my game from minimizing when I leave the screen?

Many full screen applications, particularly games, automatically minimize when they're no longer the active (foreground) application on Microsoft Windows. The Synergy server normally becomes the foreground when you switch to another screen in order to more reliably capture all user input causing those full screen applications to minimize. To prevent Synergy from stealing the foreground, in the Synergy GUI click Configure Server --> Advanced Server Options and check Don't take foreground window on Windows servers. If you turn this on then be aware that Synergy may not function correctly when certain programs, particularly the command prompt, are the foreground when you switch to other screens. Simply make a different program the foreground before switching to work around that.

Why doesn't Ctrl+Alt+Del work on secondary screens?

Source: Enabling CTRL-ALT-DEL in Windows 7 over Synergy

Using a Windows Vista or newer machine as a client: With the default Windows settings you can not enter a Ctrl+Alt+Del SAS (Secure Attention Sequence) over Synergy on the Windows lock screen. This can be frustrating if you lock your computer frequently or log in remotely.

You can allow this behavior by allowing Services to issue the SAS in the Windows Logon Options. These are found in the Local Group Policy Editor.

  1. Go to the Local Group Policy Editor (Type gpedit.msc in the run menu)
  2. Dig down to Computer Configuration --> Administrative Templates --> Windows Components --> Windows Logon Options
  3. Open up the Disable or enable software Secure Attention Sequence option
  4. Set it to Enabled and then select Services and Ease of Access applications below, click OK
You should now be able to issue a Ctrl+Alt+Del to Windows over Synergy while on the lock screen. Note: Sometimes the Ctrl and Alt keys stick, just press them each once to un-stick them.

On Windows servers, Ctrl+Alt+Del is always intercepted by Windows and is never passed to Synergy. We have implemented Ctrl+Alt+Pause/Break as a workaround, which will send a Ctrl+Alt+Del sequence across to the client. Note that the cursor must still be moved over to the client system for this to work.

On Mac laptops, the key labeled Delete is actually backspace and Ctrl+Cmd+Del won't work. However Fn+Delete really is Delete so Fn+Ctrl+Cmd+Delete will act as Ctrl+Alt+Del on a windows secondary screen.

Why do my Caps Lock, Num-Lock, and Scroll Lock keys act funny?

Some systems treat the Caps Lock, Num-Lock, and Scroll Lock keys differently than all the others. Whereas most keys report going down when physically pressed and going up when physically released, on these systems the Caps Lock and Num Lock keys report going down when being activated and going up when being deactivated. That is, when you press and release, say, Caps Lock to activate it, it only reports going down, and when you press and release to deactivate it, it only reports going up. This confuses Synergy.

There are options to fix this in the GUI settings. Or, if you use a configuration file, in the screens section, following each screen that has the problem, any or all of these lines as appropriate:

 halfDuplexCapsLock = true
 halfDuplexNumLock = true
 halfDuplexScrollLock = true

Then restart Synergy on the server or reload the configuration.

Does AltGr/Mode-Switch/ISO\_Level3\_Shift work?

Synergy does support the AltGr button, but not to the same level as other, more common modifier keys. There is a bug in more recent versions which breaks this for some users; we plan to investigate this as soon as we get a chance. Patches thoughtfully considered.

The screen saver never starts. Why not?

Different platforms have different causes. Linux: The screen saver will not start while the mouse is on a client screen. This is a consequence of how X Windows, Synergy and xscreensaver work. Windows/Mac: This can result from a bug in the Screen Saver Sync feature. It doesn't happen to everyone, but turn this feature off (Configure Server --> Advanced Server Options) and reboot to fix it.

Getting Help

How can I send my Synergy log content?

It's easy to send us your log content so that we can help debug an issue. First, turn up the logging level (for most cases) to at least Debug. In the Synergy GUI, go to Edit -> Settings (on Windows/Linux) or Synergy -> Preferences (on Mac). Find the option labeled Logging level:, choose Debug and click OK. Then, click Apply.

In the Log output area, you can Select All highlight the log content to copy the entire log. However, for most troubleshooting the log content we need is just the lines from the time period of the issue (Synergy disconnect, failure to copy from remote clipboard...). You can paste your results on Pastebin and send us the link, or if just a few dozen lines or less simply copy the content into your email, Google Group message, or forum post.


My client can't connect. What's wrong?

Usually when the client can't connect, it will give you a reason. Some common ones are things like Connection timed out or Connection refused. Some things to check are that the correct Server IP is entered (uncheck auto config if you need to override) and whether there is a firewall in the way. Also make sure the Synergy server is running and not giving any serious error messages.

Why doesn't my keyboard work on the client?

This assumes that the mouse does work on the client. This most often happens on Mac OSX. There is an option for Secure Keyboard Entry that seems to be put into effect whether the user selects it or not. If you run SecureAnywhere, it does this too. Open the Terminal app, and then pull down the Terminal menu. You'll see the option listed here. If it's checked, uncheck it. If it's unchecked, check it, and then uncheck it again.

Another possibility is that Synergy is not finding the right keyboard layout on the client. In this case, setting the logging level on the client to "Debug1" may show "can't find keyboard layout" messages. If this happens with a Windows client, go to the Control Panel, look for "Change Keyboards", and check what keyboards are listed as input language services. You may need to add a layout, such as the "US" layout for English.

What does Cannot initialize hook library mean?

This error can occur on a Synergy server running on a Microsoft Windows operating system. It means that Synergy is already running or possibly was not shut down properly. If it's running then first end the Synergy task. If it's not then try logging off and back on or rebooting then starting Synergy again.

I get the error Xlib: No protocol specified. Why?

You're running Synergy without authorization to connect to the X display. Typically the reason is running Synergy as root when logged in as non-root. Just run Synergy as the same user that's logged in.

Linking fails on Solaris. What's wrong?

Did you add

 --x-includes=/usr/openwin/include --x-libraries=/usr/openwin/lib the configure command line? Solaris puts the X11 includes and libraries in an unusual place and the above lets Synergy find them.

I can't switch screens anymore for no apparent reason. Why?

Check that your Scroll Lock is not turned on. Also check that your screen icons on your Configure Server grid share an edge.

The cursor goes to secondary screen but won't come back. Why?

Check your Scroll Lock key status. If this key is activated, Synergy will not switch screens.

There is a bug involving Windows 8/10 and high-resolution screens. When it uses Desktop Display Scaling, Synergy is no longer able to read the mouse position correctly, and the cursor ends up stuck in the lower-right corner of the client (and invisible for some reason). You can tell if this is your case by right-clicking and see where the menu appears. See the bug here.

If you have written your configuration file from scratch, you must indicate the neighbors of every screen. Just because you've configured Apple to be to the left of Orange does not mean that Orange is to the right of Apple. You must provide both in the configuration.

The cursor wraps from one edge of the screen to the opposite. Why?

Double-check your screen arrangement in the grid. In the Synergy GUI click Configure Server and make sure the screens are arranged in the same way that they are set up on your desk.

If you're using a configuration file, check your links to make sure they point to the screen you intend. If you list Orange to be to the left of Orange then moving the mouse off the left edge of Orange will make it jump to the right edge. Remove the offending line from the configuration if you don't want that behavior.

Cursor Stuck in bottom corner of machine on windows

On Windows machines with HiDPI screens, Synergy malfunctions. To fix this, change the compatibility mode for the synergys.exe and syngergyc.exe to Deactivate scaling for hiDPI and run as Windows 7 for All Users. More information can be found in the GitHub issue.

I've updated to Fedora 25 and Synergy no longer works?

This is because Fedora 25 has switched to use Wayland by default instead of Xorg server. You can re-enable Xorg as a temporary workaround by editing /etc/gdm/custom.conf and changing line 5 per line 4.

You'll then need to reboot. This has the machine fall back onto Xorg for the session manager.

 # Uncoment the line below to force the login screen to use Xorg