VNC Connect Error Messages

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Connectivity error messages

VNC Viewer may display the following error messages if a connection attempt to VNC Server running on a remote computer fails.

For server parameters, see VNC Server Parameter Reference

For viewer parameters, see VNC Viewer Parameter Reference

Error message This may occur because... Resolution

VNC Server is not currently listening for cloud connections

RealVNC services cannot establish a connection between your device and the remote computer. See Why is VNC Server not currently listening for Cloud connections?

Either the username was not recognised or the password was incorrect

You have not provided the authentication credentials that VNC Server is expecting.

If you have a Professional or Enterprise subscription, enter the user name and password you normally use to log in to your user account on the remote computer.

See What username and password do I enter when I'm trying to connect to VNC Server?

The username you have entered does not identify the domain. Prefix the user name with a domain name, for example DEV.ACMECORP.COM\johndoe

Access is Denied

The username you have provided does not have permission to connect to VNC Server.

See Why do I get an "Access is denied" error message when connecting to VNC Server?

Too many security failures

You have entered incorrect authentication credentials too many times.

Wait for the number of seconds specified by the VNC Server BlacklistTimeout parameter (10 by default)

See Too many security failures

The connection was refused by the host computer

VNC Server is either not running, or not running on the specified port. Ensure VNC Server is running. If you are establishing a direct connection and have specified a port other than the default for VNC (5900), ensure VNC Server is configured to use that port.

Connection rejected by VNC Server computer user

VNC Server is configured to require the remote computer user to manually accept or reject connections, and you have either been rejected or that user is not there.

Ensure the remote computer user is present and accepts your connection.

On the remote computer, you can turn this feature off by configuring the VNC Server QueryConnect parameter, or the Permissions parameter to automatically accept your connections.

Account locked

The system account you are trying to authenticate with has been locked on the remote computer. You will need to unlock your account on the remote computer you are connecting to. If the remote computer is managed by a domain, please contact your IT department. The account lock is not controlled by VNC Connect.

Password must be changed

The password for the system account you are authenticating with has expired and needs to be reset. You will need to reset your password on the remote computer you are connecting to. If the remote computer is managed by a domain, please contact your IT department. System passwords cannot be reset remotely using VNC Connect.

Access denied to VNC Server; please sign in to connect

You have been signed out of VNC Viewer See Why do I get an "Access denied to VNC Server; please sign in to connect" error message when trying to connect to a VNC Server?
Hosted Application error: HTTP Unauthorized You have been signed out of VNC Viewer Follow the same steps as: Why do I get an "Access denied to VNC Server; please sign in to connect" error message when trying to connect to a VNC Server?
Hosted Peer-to-Peer error: Connectivity could not be established Your firewall or proxy is blocking VNC Viewer or VNC Server from connecting to the VNC Connect cloud Make sure that you whitelist all the RealVNC services listed on the network access requirements page in your firewall or proxy settings

The connection closed unexpectedly

VNC Server is blocking your connection attempt. On the remote computer, ensure the VNC Server IpClientAddresses parameter is not blocking your computer’s IP address.
VNC Server’s private key is missing or corrupt.

You should investigate why this has occurred. On a remote Mac or Linux computer, note the location of the private key is determined by the VNC Server RsaPrivateKeyFile parameter.

You can restart VNC Server to regenerate the private key, or alternatively at the command line without restarting by running <server-binary>-service -generatekeys.

The remote computer is running Windows and the Event Log is full. On the remote computer, type eventvwr into the Start menu and then select Windows Logs > Application > Clear Log. Finally, select Properties > Overwrite events as needed.

Connection reset by peer (10054)

Your network hardware is misconfigured or faulty (this error is not specific to VNC). Run the command ping -t -l 1350 <remote-ip>to confirm the two computers can communicate with one another, without packet loss.
Your network’s MTU has changed from the default (1500 bytes). It may have been configured manually (usually within router settings), or because you are connecting over a VPN. Using fixed IP addresses rather than DHCP-assigned addresses in your router settings has been known to resolve this issue.

Connection aborted (10053)

The remote computer aborted the connection, possibly due to a data transmission timeout, or a protocol error. On the remote computer, type eventvwr into the Start menu, select Windows Logs > Application, and examine VNC Server events.

Unable to connect to VNC Server using your chosen security setting.

Either upgrade VNC Server to a more recent version from RealVNC, or select a weaker level of encryption

(Previously: No Matching Security Types)

VNC Viewer and VNC Server have incompatible encryption settings for a direct connection.

Either:

  • On the remote computer, change the VNC Server Encryption parameter to something other than AlwaysOff, or
  • Change the VNC Viewer Encryption parameter to ServerPreferOn or PreferOff.
The remote computer is running a legacy VNC Server (4.x or 5.x) or third party VNC-compatible software that does not support encryption. Either install the latest version of VNC Connect on the remote computer, or change the VNC Viewer Encryption parameter to either ServerPreferOn or PreferOff.

The event log is full

The remote computer is running Windows and the Event Log is full. On the remote computer, type eventvwr into the Start menu and then select Windows Logs > Application > Clear Log. Finally, select Properties > Overwrite events as needed.

Error (11001)

The remote computer does not exist on the IP address or hostname you have entered. Ensure you are entering the correct IP address or hostname.
The remote computer’s antivirus software or firewall is blocking your connection attempt. On the remote computer, ensure antivirus software lists VNC Server as an exception, and the firewall is configured to allow access on VNC Server’s listening port (5900 by default).

Timed out waiting for a response from the computer.

No response was received from the specified IP address, even to reject the connection.

Check the remote computer is switched on. Ensure antivirus software lists VNC Server as an exception, and the firewall is configured to allow access on VNC Server’s listening port (5900 by default).

See  if you are attempting to establish a direct connection over the Internet.

No such host is known / No route to the host is known

No response was received from the specified IP address, even to reject the connection.

Check the remote computer is switched on. Ensure antivirus software lists VNC Server as an exception, and the firewall is configured to allow access on VNC Server’s listening port (5900 by default).

Follow Setting up a direct connection over the Internet on All About Direct Connections  if you are attempting to establish a direct connection over the Internet.

The requested name is valid, but no data of the requested type was found (11004)

There is a name resolution issue within your network environment (this is a Winsock error). Enter the remote computer’s IP address rather than its host or domain name.

connect: No connection could be made because the target machine actively refused it (10061)

A remote computer user is attempting to reverse-connect from VNC Server to you, but VNC Viewer is not in listening mode. To put VNC Viewer in listening mode, run the appropriate command for your platform. Then, ask the remote computer user to connect again.

An attempt was made to access a socket in a way forbidden by its access permissions (10013)

The remote computer’s antivirus software or firewall is blocking your connection attempt. On the remote computer, ensure antivirus software lists VNC Server as an exception, and the firewall is configured to allow access on VNC Server’s listening port (5900 by default).
Another application or service is listening on the same port as VNC Server. On the remote computer, ensure the TCP port on which VNC Server is listening for direct connections (identified by the RfbPort parameter) is not in use by any other application or service.

VNC Server error messages

VNC Server may display the following error messages.

Error message This may occur because... Resolution
Hosted Bootstrap error: Network failure: Error connecting: Proxy error via <customer proxy>: AuthenticationRequired (AuthenticationRequired) You are adding a computer to a team but there’s an intermediate proxy server. Refer to Negotiating proxy servers on All About Cloud Connections

Invalid date (0-0-0T0:0:0)

You are attempting to license VNC Server on a computer that has incorrect date/time settings. Ensure a valid time zone is set on the computer, for example using Microsoft’s tzutil.exe tool.

VNCServer has failed to launch - Mac OS X

Another process is listening on the same port as VNC Server (by default 5900). The VNC Server tray icon may also disappear. Disable other remote control/screen sharing applications, then restart VNC Server.

Secure encryption key is missing or corrupt

VNC Server does not have a private RSA key.

Run the following command to generate a RSA key under Windows:

vncserver.exe -service -generatekeys (Service Mode)

vncserver.exe -generatekeys (User Mode)

XML error 0:0 Error: First Tag not found

You are attempting to license VNC Server, and Windows Event Log is full. Type eventvwr into the Start menu and then select Windows Logs > Application > Clear Log. Finally, select Properties > Overwrite events as needed.

Could not open default font ‘fixed’ - UNIX

The computer’s default font path is not valid for Xvnc.

Run xset q to list information about your X Server, including the font path you should use.

Specify the -fp X option in the appropriate vncserver configuration file, and append the font path, for example:

-fp "/usr/share/fonts/Xll/misc,built-ins"

The appropriate file is /etc/vnc/config for all users, and ~/.vnc/config for the currently logged-in user.

Could not run xauth

This means that the xauth program was not found. This is needed to start a VNC® Server desktop, but is often not on root's PATH. You will need to add the appropriate directory to your PATH.

When the software was installed, it will probably have flagged a warning that xauth was not on the PATH and indicated where it was. If it did not, or this information was not recorded, then running the following command as a non-root user may locate the binary:

which xauth

Another cause of this error could be if xauth is unable to resolve the hostname. You can check that your hostname is resolvable by running:

host myservername

This should return an IP address. If this is not the case, you need to set this up by adding the machine's IP address followed by the hostname to the /etc/hosts file (this is normally done automatically if you are using DHCP).

If you are on an office network with a DNS server, you should contact your system administrator.

Unspecified GSS failure

There is a conflict between the GSSAPI library and the CUPS shared library on the VNC Server computer

Disable CUPS:

chmod -x /usr/lib/cups/backend/vnc

This will prevent VNC from loading libcups. SSO should now work, though remote printing will not. Note that just disabling printing is not enough.

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