If the recommended resolution does not fix your problem, or if you cannot find your error message, please contact our Support team.
Connectivity
RealVNC Viewer may display the following error messages if a connection attempt to RealVNC Server running on a remote computer fails.
For RealVNC Server parameters, see VNC Server Parameter Reference
For RealVNC Viewer parameters, see VNC Viewer Parameter Reference
| Error message | This may occur because... | Resolution |
|---|---|---|
|
Too many existing concurrent sessions |
You have reached your plan's maximum number of concurrent sessions. |
To make a new connection, you will need to first end one of your existing sessions. See Viewing and managing remote access sessions
|
|
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? |
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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
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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? |
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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) |
|
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 your connection request has been rejected. |
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. |
| The VNC Server computer user did not respond to the connection request
|
VNC Server is configured to require the remote computer user to manually accept or reject connections and the user is not there to accept (or reject) your connection request. |
Ensure the remote computer user is present and accepts your connection. If you need to access the remote computer when there isn't a user present, you can turn this feature off by disabling the "Show accept/reject prompt" setting in RealVNC Server's Options, Connections section, or disabling QueryConnect parameter in the Expert section. Alternatively, in VNC Server's Options, Users & Permissions section, configure the permissions for your user to automatically bypass the connection prompts. |
|
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. |
| 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. |
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| 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. |
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|
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 |
VNC Viewer and VNC Server have incompatible encryption settings for a direct connection. |
Either:
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| 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 Server, PreferOn or PreferOff. |
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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 remote computer, even to reject the connection. |
You are trying to establish a direct connection to a RealVNC Server that is licensed with a subscription that allows cloud connections only. |
|
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. |
||
|
No such host is known |
VNC Viewer was unable to determine an IP address for the specified computer name. |
If you are trying to use a cloud connection, make sure you are signed in to VNC Viewer and use the entry for your computer under the Team heading in VNC Viewer. Otherwise, if you are trying to use a direct connection (Enterprise only), check that the computer name resolves to an IP address e.g. using nslookup. |
|
No route to the host is known |
VNC Viewer does not have a network route to connect to the specified computer name/IP address. |
This error usually occurs when the IP address belongs to a different network to the network VNC Viewer is running on. Check that the computer name resolves to the correct IP address e.g. using nslookup. |
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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. |
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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. |
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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 Viewer is not licensed to connect to this VNC Server
|
VNC Viewer is connecting to a VNC Server that is licensed with a per user subscription, and is either not part of the same team as the VNC Server, or is an incompatible version. |
Check you are using VNC Viewer 7.x or later. Ensure you are signed into VNC Viewer, and the account you have signed in with is joined to the same team as VNC Server. If you are using VNC Viewer offline, ensure you have applied an offline license to VNC Viewer. |
RealVNC Server
| 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:
|
|
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 Specify the
The appropriate file is |
|
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:
This will prevent VNC from loading libcups. SSO should now work, though remote printing will not. Note that just disabling printing is not enough. |
RealVNC Server for Mobile
| Error Code / Message | This may occur because... | Resolution |
|---|---|---|
|
Invalid configuration. Please contact system admin. (100) |
Both joinCloud and leaveCloud parameters have been defined in an MDM configuration policy. | Ask your system administrator to check they have not configured both joinCloud and leaveCloud in the MDM configuration for RealVNC Server for Mobile. |
RealVNC Connect Setup app
All platforms
| Error Code / Message | This may occur because... | Resolution |
|---|---|---|
|
X.509 Error: Certificate expired |
A web filter or proxy is in use on your computer. |
Check that the IP addresses and domains in this article are not blocked on your network. Otherwise, try using the below offline installers instead. |
Windows
| Error Code / Message | This may occur because... | Resolution |
|---|---|---|
|
1602 |
The user cancelled installation | Try the installation again. |
|
1603 |
A fatal error occurred during installation |
Check Event Viewer - Administrative Events for more details of the error. You can also try using the offline installers instead, which you can download using the links below. |
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