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Is there any way to change it from the default 5900 to some other port?

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At least disable connections from everything except localhost to 5900; Securing OS X with ipfw - CS Labs Wiki –  user104072 Nov 4 '11 at 1:25

4 Answers 4

up vote 12 down vote accepted

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
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If you're still around -- once you've done this, is there a comparable way to get the built-in Mac screensharing app to connect to that port, or are you stuck using third-party vnc apps that let you specify the port? –  Jim Miller Sep 19 '13 at 14:11
1  
Answer to above: In "Connect to server...", specify vnc://yourserver.com:54321 (following the earlier example re port number) –  Jim Miller Sep 19 '13 at 14:36
    
If this works (I can't check until tonight) you deserve a whole lot more upvotes. –  PaulSkinner Oct 11 '13 at 10:14
    
Incidentally, it does. Confirmed working flawlessly. I would guess you will probably have to redo these steps after each OS update, but still... –  PaulSkinner Oct 14 '13 at 19:37
1  
To confirm, yes you would need to do this after each OS update (including incremental updates). –  PaulSkinner Oct 24 '13 at 6:54

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.
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Just for the sake of completeness: some suggest that changing the ports in /etc/Services might do the trick. I tried that (I even rebooted my Mac after changing it) to no avail. And giving it some more thought, it might even be a bad idea to mess with that file, as other applications might also use it to get the well-known port number if they want to connect to some third-party using a specific protocol. (Like: changing the SSH port in that file might seem to work but is a bad idea.) –  Arjan Dec 1 '10 at 11:07
1  
Note the answer by Greg Canty -- it can be changed on OS X releases after Snow Leopard. This answer was originally written before OS X Lion was released. –  Doug Harris Nov 21 '13 at 18:36

I can confirm after finding this thread via Google that editing /ect/services for the "rfb" ports will redirect 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.

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Based on the info provided by Greg in this thread I wrote a bash script that will automate the process of changing your system's VNC listening port. Works well in my tests. Let me know if anyone has any issues with it.

#!/bin/sh

#If you find it useful (or have suggestions, feedback, etc.), shoot me an email at throwapenny@me.com.
#Requires Mac OS 10.7.x or later (tested up to and including 10.10.3)

#Setting Static Variables
sourcepath="/System/Library/LaunchDaemons/"
filename="com.apple.screensharing.plist"
port=`less $sourcepath$filename | awk 'f{print $1;f=0} /SockServiceName/ {f=1}' | awk -F "<|>" '{print $3}'`
os_version=`sw_vers -productVersion`
os_version_aug=`sw_vers -productVersion | awk -F "." '{print $1$2}'`


clear
echo "---------------------------------------------------------------"
echo "---                                                         ---"
echo "--- This Script Will Change Your Systems VNC Listening Port ---"
echo "---             Hit Ctrl + c to Exit At Anytime             ---"
echo "---                                                         ---"
echo "---------------------------------------------------------------"

#Check System Version
sleep 1
if [ "${os_version_aug}" -lt "107" ]; then
echo ""
echo "System OS Must Be 10.7.x or Greater.  Aborting Script."
exit 0
else
echo ""
echo "System OS Version is" $os_version
echo "OS Requirement Met √"
echo "--------"
fi

#Give Feedback on Current Port
sleep 1
if [ "${port}" == "vnc-server" ]; then
echo ""
echo "The System's VNC Port is Currently"
echo "Set to the System Default Port of 5900."
echo "--------"
elif [ "${port}" != "vnc-server" ]; then
echo ""
echo "The System's VNC Port is Currently"
echo "Set to a Non-default Port of" $port"."
echo "--------"
fi

#Updating Port
echo ""
printf "What Port Would You Like VNC to Listen On? "
read newport
echo ""
echo "The Following Action Requires an Admin Password."
echo "Note: Your Password Will Be Visible When You Type It"
echo ""
printf "Admin Password? "
read admin_pass
sleep 1
echo ""
echo "Created" $filename".bak."
sleep 1
echo ""
echo "Updating VNC Port to" $newport"..."
echo $admin_pass | sudo -S sed -i.bak -e "s|$port|$newport|g" $sourcepath$filename
sleep 1
echo "Done"
echo ""
sleep 1

#Restarting screensharing process
echo "Restarting Screen Sharing Service..."
sudo launchctl unload /System/Library/LaunchDaemons/com.apple.screensharing.plist
sudo launchctl load /System/Library/LaunchDaemons/com.apple.screensharing.plist
echo "Done"
sleep 1
echo ""
echo "Your System's VNC Port is Now Set to" $newport"."
echo ""
echo "Update Complete.  All Done."
exit 0
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Why not paste its code here? –  Mureinik Apr 10 at 7:13
    
When i tried to access the link - i got the error This server could not prove that it is getsome.homeftp.net; its security certificate is not trusted by your computer's operating system. This may be caused by a misconfiguration or an attacker intercepting your connection. –  Prasanna Apr 10 at 8:08
    
Sorry about that Mureinik. Code posted instead of a link. –  Will Apr 10 at 15:22

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