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Cannot Connect to XenServer from XenCenter

Michael Cropper



- XenCenter (running on a Windows PC)

- XenServer (installed via APT on Ubuntu 18.04 using the command, sudo apt-get install xen-hypervisor-4.9-amd64


I can SSH into the server fine.


Whenever I click on 'Add New Server' in XenCenter I get the error message;


"Unable to connect to server ''. The connection was refused. Check that XenServer is configured correctly on '' and try again"


It was my understanding that the 'configuration' of the XenServer was done via XenCenter once it was installed?


Any ideas? Not sure what to try to get the two talking to each other and/or debugging steps to take. 





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Thanks for the quick replies all. 


Based on what you've said, I believe I may have set this up incorrectly. Currently I have Ubuntu Server 18.04 as the main OS, which I then installed Xen on (I thought that the Xen Hypervisor 4.9 from Apt was Xen Server, not Xen, but I could be wrong - I followed this guide, https://help.ubuntu.com/community/Xen )


At the moment here is my setup;

 - 1x HDD (where Ubuntu Server 18.04 + Xen is installed as outlined above)

 - 3x HBA RAID Controller cards with RAID 6 configured for 4x other HDDs (via a software application, not via the HBA BIOS settings)


It sounds like I need to get rid of Ubuntu Server 18.04 and stick with just the Citrix Hypervisor 8.0 from the download page mentioned (I have actually had a look at that, just not installed yet, as I thought what I had done so far would work - looks like it doesn't though)


The only question I have at the moment before I go ahead with the fresh install of Citrix Hypervisor 8.0 (instead of the Ubuntu Server 18.04 + Xen setup I have at the moment) is how would I go about accessing the Web GUI control panel for the HBA RAID Controller cards once Citrix Hypervisor is installed? Rather annoyingly the HBA RAID Controller cards only support RAID 6 via the Web GUI configuration and not via the BIOS settings - and I don't want to have to go and buy some more cards. Is there a GUI that I can access via this method on the server itself, or is Xen Center technically classed as the GUI (albeit a XenServer management interface focused GUI) ?


I believe (I need to check) that I may be able to access the Web GUI for the HBA RAID Controller cards remotely, so I'll have a look into that in the meantime...... ok, looked into that, this is possible - as long as it is possible to install the Web GUI (from the command line) on Citrix Hypervisor - which I believe is possible from what I've read so far as it is my understanding that you can SSH into the box just like you would with any server. 


You wouldn't believe how much I've had to read through to get to this point of understanding about Xen - seems it's had quite a journey over the last few years and there is very little up to date information I can find around the internet about full setups. 


Also, the command 'xe-toolstack-restart' didn't work - I get the 'command not found' error. I seem to be able to run the command 'xl info'. 





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Thanks all. From what I've picked up is that the setup I had (outlined in original post) wasn't that great (Server: Unbutu Server with Xen installed via APT). 


As a follow up, I've since done a clean install of XenServer directly on the Server (which seems to be bringing other challenges, but we'll come to these as I work through those... :-) ) 


Thanks for help/pointers. 





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I have the same symptom, but my issue is different:

I just upgraded from Citrix Hypervisor 8.2 CU1 to XenServer 8 (downloaded from XenServer.com and burnt to a DVD).

I also downloaded (from XenServer.com) XenCenter 2024.1.0.

Like Michael, I can connect with SSH (using Putty from Windows), but I get "The connection was refused" from XenCenter.

Running "netstat" on Windows shows that my connection to SSH (port 22) works, but XenCenter is trying to connect to port 443 (HTTPS). Running xe-toolstack-restart does not help. Running netstat -an on the XenServer shows that it is not listening on port 443.

The other hypervisor (still running Citrix Hypervisor 8.2 CU1) is listening on port 443, so I assume XenCenter was always using port 443. The new server (XenServer 8) is not listening. Why?

Further investigation shows that Citrix Hypervisor uses stunnel to listen port 443 and tunnel to port 80 (which is probably the Xen API). XenServer 8 is running the process "stunnel -fd 7", but that isn't doing the same thing. What when wrong here?

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I'm getting closer at diagnosing the problem! I found this error:


[!] SSL_CTX_use_certificate_chain_file: ssl/ssl_rsa.c:303: error:140AB18F:SSL routines:SSL_CTX_use_certificate:ee key too small

The certificate it is complaining about is dated January 2018!

The problem seems to be that the upgrade installed a version of stunnel with TLS support that requires a more secure certificate, but it didn't generate a new certificate because the old one was already there.

I'm going to try removing it and see if it will make a new one.

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