1. You have just updated vCenter (in my case, VCenter Appliance with PSC 6.0 to 6.0U2)
2. You have restarted vCenter, waited for ~ 10 minutes and trying to open web sphere client
3. Unfortunately,error appears:
503 Service Unavailable (Failed to connect to endpoint: [N7Vmacore4Http20NamedPipeServiceSpecE:0x7fb16c058ad0]
_serverNamespace = / _isRedirect = false _pipeName =/var/run/vmware/vpxd-webserver-pipe)
OR Information message:
The vSphere Client web server is initializing
4. To fix it go to VAMI (https://<vcenter fqdn>:5480) and check overall health status.
5. To check services manually, enable SSH and BASH from html client
6. Or login to direct console (DCUI) and enable SSH/BASH from there
7. Open Putty and connect to vCenter Appliance, type root password and shell
8. Check status of services again
9. Check vSphere web client service status
service vsphere-client status
10. Try to restart or start service and check status after manipulations
To restart: service vsphere-client restart To stop and start manually: service vsphere-client stop service vsphere-client start
11. vSphere Web Service should be running and overall health indicator status is green or, at least, yellow
12. Try to open vSphere Web Client
Note: you also need to make sure that there are no issues with DNS and IP allocations in your network (DNS is available, there are no IP duplicates, firewall deny rules and etc.)
UseIT | Roman Levchenko 
I got this after changing the vCenter’s IP address
1. I used #6 https://rlevchenko.com/2016/03/24/vcenter-503-service-unavailable/ to enable the shell.
2. ssh into the vcenter server
3. Command> shell
4. vi /etc/hosts changed the IP there
5. service-control –stop –all
6. service-control –start –all
your feedback is great. thank you very much for sharing. it can be helpful for someone
Your feedback is great. Thank you very much for sharing. BR from Mexico you saved my life
I have a call with VMWare regarding this error and the above steps did not resolve the issue. We found out the problem was with our Oracle account Password has expired.
I would recommend that you look at the log files on the vCenter Appliance to find out the issue first.
1. Enable SSH and Bash for the vCenter Appliance.
2. goto /var/log/vmwre/vpx/vpxd.log-xxxx and view the log file to see the error message.
3. Press Shift+G to go to the end of the log file to see the latest error message.
Look for an error message; this should provide a clue to the problem.
Thanks for sharing your experience!