Error 1: Could Not Read From Socket: An error occurred when attempting to reading data from the connection. This error may occur because a firewall (whether an application running on the remote computer, a router's on-board firewall, or a modem's firewall) is not accepting incoming connections. Check each firewall, from the remote computer to its Internet gateway device (router, modem), to make sure that incoming VNC (and optionally, SSH, if using a secure connection) traffic is allowed.
Error 2: Could Not Write To Socket: An error occurred when attempting to send data.
Error 3: Invalid Protocol Handshake: An error occurred when attempting to communicate with the VNC server. If using a third-party VNC application, confirm that you're using a recent version and that the proper protocol version is selected (if applicable).
Error 4: Invalid Protocol Version: The VNC server returned an unexpected protocol version. If using a third-party VNC server, confirm that you're using a recent version with the proper protocol version selected (if applicable).
Error 5: Cannot Accept Connection: This may be caused by a software or hardware firewall (operating system, router or modem) refusing incoming connections. Confirm that all firewalls are configured with exceptions for incoming VNC traffic.
Error 6: Auth Type Unsupported by Framework: The VNC server requires an authentication type not supported by Screens.
Error 7: Auth Type Unsupported by Server: The VNC server doesn't support the authentication method selected in Screens. Try another authentication method in the saved screen settings.
Error 8: Auth Failure: The username or password is incorrect, or the authenticating user does not have permission to connect to the remote computer. If you're sure that the log-in credentials are accurate, check the user permissions for the VNC server. On Macs, see System Preferences > Sharing. On other systems, refer to the VNC server's configuration.
Error 9: Auth Type Missing Credentials: The VNC server expected a password, but one wasn't provided.
Less Common Errors
Error 10: Crypto Error
Error 11: Already Closed
Error 12: Invalid Message Type
Error 13: Unknown Codec Type
Error 14: Stream Error
Error 15: Codec Error
Error 16: Rect Out Of Bound
These errors can often be addressed by simply rebooting the remote computer and router/modem. Some network devices may have to be unplugged from the power source, with at least a 30-second wait before reconnecting, in order to reboot properly.