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Server: Debian testing, with the 1.4.14 deb downloaded and installed. Client: Windows 7, with 1.4.14 downloaded and installed. Both are Premium.

On Debian, start the server with synergys -f -c synergy.conf, because running it from the KDE menu makes it give an error "Option not supported on Linux: --enable-drag-drop" (and incidentally I can't find any file that might be telling it to use that option).

On Windows, run the client. Both are using encryption, with a simple password to be sure it's correct. The client says "WARNING: failed to connect to server: Protocol error from server", and the server says "NOTE: new client disconnected".

I haven't changed any configuration except the password, and 1.4.12 worked on the same machines just minutes ago.

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Maybe this would help… – sorin Oct 23 '13 at 11:22
I'm having the same problem but with 1.4.15. Server is my Macbook and client is Ubuntu 13.10. Let us know if you find a solution. – Mike Haas Oct 23 '13 at 20:36
As a side note, it works just fine when using the GUI. – Mike Haas Oct 23 '13 at 20:36
Sorin - no, both sides are using encryption, and I set a password short enough to get right! – Peter Westlake Oct 23 '13 at 22:31
I'm using 1.4.17 now, on a new machine, and that works. I never did solve the problem. – Peter Westlake May 12 '14 at 13:33
up vote 10 down vote accepted

Due to a change in the encryption protocols that Synergy uses - irrespective of server/client OS - password mis-matches can end in the following error:

synergy protocol error from server

Resetting (or removing) the password should allow successful connections.

  • Linux: Edit > Settings
  • MacOS: / Synergy > Preferences
  • Windows: Edit > Settings (?)
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This was exactly my issue; try stopping the service and resetting the password on both machines, and then restarting the service (server first, then client). – Topher Fangio Aug 13 '14 at 19:17
My issue was also encryption password related. I forgot the configure the client with the same encryption password as on the network. A more helpful error than "protocol error from server" like "decryption failed" would have been helpful though – protongun Sep 8 '14 at 16:35
Odd - I can only make it work with no password. Even a very simple password set at both ends fails. – Danny Staple Sep 17 '14 at 14:23
Newbie question: How do you reset the password in Synergy? – Nocturne Nov 3 '14 at 20:19
@Nocturne , after a lot of searching, I found the hidden menu and I've added directions above. – Alastair Jan 30 '15 at 11:27

I've been having this problem too, and here's what I did:

1) Confirmed that (Linux) client had the bold server IP entered as its server IP. Note: My server Synergy window has three IP addresses listed and one of them is bold/current.

2) Looked at the top bar of my Linux client and noticed several instances of Synergy running, so I quit all of them.

3) Stopped client and server, then started server, then started client.

Now the logs just show entering screen/leaving screen and they are calm again.

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