How to tunnel Synergy over SSH?

I know this is a long time ago but it's still appearing in search engines so I thought I'd answer.

Assuming a simple setup of one pc that you are sitting at called "parent", this is the one with the keyboard and mouse. The "child" is the one you want to connect to and it has no keyboard and mouse.

[user@parent ~]$ cat /home/user/synergy-over-ssh.conf
section: screens
  parent:
  child:
end
section: links
  parent:
    right = child
  child:
    left  = parent
end
section: options
  screenSaverSync = true
end

The first step is to run the server on the parent

[user@parent ~]$ synergy-core --server --address 127.0.0.1 -c /home/user/synergy-over-ssh.conf -n child-pc

This will start the server listening on the port 24800 on the parent.

$ netstat -anp | grep synergy
tcp        0      0 127.0.0.1:24800         0.0.0.0:*               LISTEN      3290/synergy-core

Now we need to connect from the parent to the child, but we then need to send back from the child port 24800 to the port 24800 on the parent.

[user@parent ~]$ ssh child-user@child -R 127.0.0.1:5900:127.0.0.1:5900
[child-user@child ~]$ 

On the child you will want to run the client and tell it to connect to the localhost or 127.0.0.1

synergy-core --client --name child 127.0.0.1

Now on the parent you should be able to scroll your mouse to the right off the parent screen and (appear to) move it to the child screen.

You can make this more permanent by adding an entry in your ~/.ssh/config file

[user@parent ~]$ cat /home/user/.ssh/config
Host child
  user child-user
  Hostname ip.or.host.of.child.pc
  RemoteForward 127.0.0.1:24800 127.0.0.1:24800

Which would then allow

[user@parent ~]$ ssh child
[child-user@child ~]$ 

You can automate the entire thing by creating a script that does a clean start of synergy, then connects to the child in the background without opening a ssh terminal the "-N" option.

#!/bin/bash
killall synergy-core
synergy-core --server --address 127.0.0.1 -c /home/user/synergy-over-ssh.conf -n child-pc
ssh -N child >/dev/null 2>&1 & 

On the client you should have a autostart script like $ cat ~/bin/startsynergy.sh #!/bin/bash killall synergy-core sleep 2 synergy-core --client --name child 127.0.0.1 exit 0

Note that on older versions replace synergy-core --server with synergys, and synergy-core --client with synergyc.

One disadvantage of this method is that copy and paste will not work unless you start the client using the keyboard on the child pc.