How to change the default screen sharing / VNC port number on Mac OS X?

You actually can switch the default port for Apple's VNC server on Mac OS 10.7 Lion and 10.8 Mountain Lion. To change the port, you need to edit the server's plist file /System/Library/LaunchDaemons/com.apple.screensharing.plist (this file doesn't exist in systems prior to 10.7 Lion).

Editing the file requires root (sudo) privileges. In the terminal, if you are familiar with vi or vim, you can type:

sudo vim /System/Library/LaunchDaemons/com.apple.screensharing.plist

or if you're not, you'd better use nano:

sudo nano /System/Library/LaunchDaemons/com.apple.screensharing.plist

Now, all you have to do is change line 34 (the one that reads <string>vnc-server</string>) to <string>nnnn</string> where nnnn is the port number you wish to use. I know it seems weird changing a name like "vnc-server" to a number, but that's the way you have to do it. I've included an example below in case anything's not clear.

To change the default port to 54321, you would edit the plist file to look like this:

...
<key>Sockets</key>
  <dict>
      <key>Listener</key>
      <dict>
          <key>Bonjour</key>
          <string>rfb</string>
          <key>SockServiceName</key>
          <string>54321</string>            <!-- Change this line! -->
      </dict>
  </dict>
  <key>UserName</key>
  <string>root</string>
  <key>SHAuthorizationRight</key>
  <string>system.preferences</string>
</dict>
</plist>

After saving the file, to make the change take effect, turn Screen Sharing off and then on again in the Sharing preference pane, or alternatively unload and re-load the service using these commands:

sudo launchctl unload /System/Library/LaunchDaemons/com.apple.screensharing.plist
sudo launchctl load /System/Library/LaunchDaemons/com.apple.screensharing.plist

I can confirm after finding this thread via Google that editing /etc/services for the "rfb" ports will change the included VNC server's listening ports.

I edited the file and rebooted (usually I'd try restarting services or unloading the launchdeamon but I was having some other issues as well and didn't bother). iTeleport on my iPad then failed to connect on 5900 and succeeded on the high unprivileged port I chose.

This has been discussed on various forums at apple.com and on macosxhints.com. The short answer is "you can't change it".

The longer answers suggest ways around it -- three possibilities:

• Use alternate VNC server software
• Use an ssh tunnel to redirect traffic from your custom port to 5900
• Configure port mapping in your router to take incoming traffic on a different port to go to port 5900 on your mac.