OpenColor Connection: "Host unreachable"

Problem description

GMG ColorPlugin cannot connect to GMG OpenColor, and the preferences dialog shows the status: “OpenColor: Host unreachable”.

Prerequisite: Check if OpenColor can be reached

Open the remote Client in order to check in general if the connection to OpenColor is possible.  

• If the connection is possible, please proceed with allowing the applications to connect to GMG OpenColor..
• If the remote Client does not display data, please check if OpenColor is running. Additionally, check if the port is free.

Allow Adobe PhotoShop/Illustrator to connect to GMG OpenColor

Check the Local Network Settings

MacOS rules might block outgoing connections from Adobe Photoshop/Illustrator. 

1. First please close the Adobe applications
2. Now please open the local network settings: System Settings → Privacy & Security → Local Network
3. Here all applications that have attempted to establish an outgoing connection are listed. 
   --> If the slider is set to disabled, please set it to enabled (to allow the connection). 
   --> If the slider is set to ‘enabled’, disable it once, wait a moment and then re-enable it. 
   

Notes:

• The connection issue occurs independently from the macOS firewall. The macOS firewall only controls incoming connections. However, since the plugins initiate outgoing connections to OpenColor, this problem can happen equally on systems with disabled as well as with activated firewall. 
• Enabling port 8080 TCP on the Windows side is, of course, necessary.

Delete the list of applications in the local network settings

If the enabling the application as described above does not help, or if the Adobe Photoshop/Illustrator applications are listed multiple times in the list, this is a macOS bug and we recommend cleaning the list.

Before you start, please make sure, you have the following at hand:

• User name and password with administrative rights for your Mac 
• A description how to boot in recovery mode, e.g.
  Recovery mode for Macs with Apple silicon (M1/2/3/etc.) 
  Recovery mode for Intel-based Macs

Steps

1. Start up your Mac in recovery mode
2. Disable the 'System Integrity Protection' temporarily by opening Menu → Utilities →  Terminal and enter csrutil disable 
3. Reboot
4. Delete the following files 
   /Library/Preferences/com.apple.networkextension.plist
   /Library/Preferences/com.apple.networkextension.uuidcache.plist
5. Reboot
6. Relaunch PS and/or AI. 
7. Allow the outgoing connection for Adobe Photoshop/Illustrator
   
   If the above message does not pop up, allow Adobe Photoshop/Illustrator manually in:  System Settings → Privacy & Security → Local Network
8. Verify that the list of applications in the local network settings only contains a single entry now. 
9. Shutdown and start up Mac in recovery mode
10. Enable the 'System Integrity Protection' by opening Menu → Utilities →  Terminal and enter csrutil enable
11. Reboot