I posted about this same error message sometime back but now I have discovered an easier and faster way to resolve it. Not fix it permanently, mind you, but at least make it so you can connect to your vSphere server using the VMware vSphere Client.
The Problem
When you are trying to logon to your vSphere 5 server using the VMware vSphere Client you get an error that says, "The remote server returned an error: (503) Server Unavailable".
The Problem
When you are trying to logon to your vSphere 5 server using the VMware vSphere Client you get an error that says, "The remote server returned an error: (503) Server Unavailable".
The Solution
Assuming you have enabled SSH on your vSphere server you can open a Putty session on port 22. After you have connected and logged in as root, issue the command called dcui and this will launch a console session that looks just like you were standing at the server.
Assuming you have enabled SSH on your vSphere server you can open a Putty session on port 22. After you have connected and logged in as root, issue the command called dcui and this will launch a console session that looks just like you were standing at the server.
Click F2 and login as root
Choose Troubleshooting Options from the menu
Choose Restart Management Agents from the menu
Press F11 to confirm your choice
Once the services are restarted you should now be able to login using the vSphere Client.
There have been times when I've had to restart the Management Agents multiple times before I could finally get the vSphere Client to work. I was hoping this would be resolved with VMware vSphere 5 Update 1, but unfortunately it has not. And this is only occurring for me on one vSphere server whereas we have five others that are behaving fine.
