I had a day when users were unable to start their VDI instance and when I tried to check the VM's XenCenter refuses to connect as all.
You could ping the server fine and even access it by SSH with no issue.
Turns out some VM's got stuck and XenServer basically stopped processing anything from the the delivery controller. This also caused me losing access to the servers through XenCenter.
The fix is to simply restart the Toolstack.
- SSH Into the XenServer Master
- Enter the following command: xe-toolstack-restart
- You should see the progress immediately, once it's done try connecting again. Sometimes it takes a while before it makes the connection but it shouldn't error out anymore.