Are you getting the error ‘The connection closed unexpectedly’ on your VNC Viewer? Here’s how we fix it.

Usually, this error shows up when the VNC server is blocking the connection or if the server’s private key is missing.

At Bobcares, we often get requests to fix VNC errors, as a part of our Server Management Services.

Today, let’s have a look at this VNC error and see how our Support Engineers fix it.

Why does VNC viewer show ‘The connection closed unexpectedly’?

Usually, the VNC Viewer shows error messages when the connection to the remote VNC server fails. One such error message is The connection closed unexpectedly.

And the error message in the VNC viewer appears as,

The possible reasons for this error are:

• The VNC server is blocking the attempt to connect.
• A corrupted or missing private key of the VNC server.
• A remote Windows server with a full event log.

Now let’s see how these errors can cause the connection to close. We will also see how our Support Engineers fix this error.

How we fix the error VNC connection closed unexpectedly?

Whenever our customers approach us with this error, our Support Engineers check for the possible reasons for this error.

1. Check the remote VNC server settings

In some cases, the parameters defined in the remote VNC server can end up in error.

So, our Support Engineers check the parameters in the remote VNC server. We ensure that the IpClientAddresses is not blocking the local machine running the VNC viewer.

2. The corrupted private key that closes the VNC connection unexpectedly

Similarly, any error related to the private key of the server can also close the VNC connection.

So, our Support Engineers check the private key. We check the location of this private key file defined in the RsaPrivateKeyFile.

If there is an error in the private key we can regenerate it. This can be easily done by restarting the VNC server.

Alternatively, we can regenerate the key using the command,

<server-binary>-service -generatekeys

3. Event log in Windows becomes full

Another possible reason for this error in the Windows server is a big event log. So in the remote Window VNC server, we check the log. The fix is to clear the log. For this, we navigate as Windows Logs >> Application >> Clear Log.

In addition, we overwrite events in Properties if needed.

4. Other possible reasons

Sometimes outdated versions of VNC viewer or version mismatch between server and client can also end up in error.

Similarly, firewall rules can block both the port and IP address of the server in the local machine running VNC Viewer.

[Need assistance in fixing VNC errors? – We will help you.]

Conclusion

In short, the error VNC connection closed unexpectedly can occur due to many reasons. The possible reasons are remote VNC server settings, missing or corrupted private key, full event log in Windows server, firewall rules, etc. In today’s write up we saw how our Support Engineers fix this error.