VMware vSphere: HTML5 Webclient returns 503 Service Unavailable (Failed to connect to endpoint)


last week I upgraded an vSphere instance from vSphere 6 to vSphere 6.7.

The upgrade process completes without any errors.

I tried to connect to the new HTML5 frontend but always getting an error:

503 Service Unavailable (Failed to connect to endpoint: [class Vmacore::Http::LocalServiceSpec:0x000000c7343c7a90] _serverNamespace = /ui action = Allow _port = 5090)

while the flash frontend works fine. After some investigation I found the solution for this issue. The following steps describes this process (maybe this helps if someone got an similar error).

I tried to start the HTML5 frontend from command line.

D:> "C:\program files\VMware\vCenter Server\vmon\vmon-cli.exe" -r vsphere-ui
Start service request failed. Error: Service crashed while starting

Then I used the process monitor to get the processname and the complete command line. I found out that the UI is based on java.

The process monitor gives me the complete commannnd line to start the HTML5 webclient. I openend a cmd.exe shell, copied the command line and start it (its too long to completly show it here)

D:>"C:\program files\VMware\vCenter Server\jre\/bin/java" -Xmx1568m -XX:Compress
edClassSpaceSize=256m -Xss320k -XX:ParallelGCThreads=4 -Djava.io.tmpdir=...

After scrolling several command line output pages I found the following exception:

SEVERE: StandardServer.await: create[localhost:8005]:
java.net.BindException: Address already in use: JVM_Bind

The TCP port to which the HTML5 Service wants to bind to is occupied. TCPView shows that Tomcat Process has the port 8005 already in use.

Tomcat Service stopped and tried to start the UI:

D:> "C:\program files\VMware\vCenter Server\vmon\vmon-cli.exe" -r vsphere-ui
Completed Restart service request.

And it works 🙂


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2 thoughts on “VMware vSphere: HTML5 Webclient returns 503 Service Unavailable (Failed to connect to endpoint)”

  1. Hi Michael,

    FYI that VMware has released a KB article that provides more insights on the possible root causes and troubleshooting steps. For more information, see KB 67818 “503 Service Unavailable” error on the vSphere Web Client when logging in or accessing the vCenter Server”.

    Thank you.

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