Please use the port which is not busy by WCS. 8081 is not suitable because it required a lot of configuration changes (Can we configure ssh on 8081 port as the ssh 22 port is not exposed via internet?
You can also use a port from media ports range (31001-32000) if TCP ports are opened. WCS just skips the port if it is busy by another application.
If you can't set up SSH access to the server, please deploy a staging one with the same hardware configuration, reproduce the problem and provide SSH acccess to the staging instance.
If this is not possible, please reproduce the problem using demo example and collect a report as described here including client debug logs. Report archive should be collected by report.sh script. Then, send the report using this form.