Register-SPWorkflowService : The Underlying connections was closed: An unexpected error occured.

This issue occurs when we run power shell command to register workflow manager service after successfully installing and configuring Workflow Manager in SharePoint 2013.

The primary reason of getting this error is incorrect Power Shell command format. Make sure if your workflow manager service is configured on https then use https in workflow manager site url and also make sure to mention domainname.com in your workflow manager site url to make Power Shell work properly.

In the above command I have not used https in my –workflowHostUri and also I have not associated domain name in my –workflowHostUri parameter.

Now, I have rectified this after changing the Power Shell command and it worked for me.

  

So, the correct Power Shell command should be as under:

Register-SPWorkflowService –SPSite "http://SPSERVER2012" –WorkflowHostUri "https://SPSERVER2012.SPDOMAIN.com:12290/" –AllowOAuthHttp

Once this command executes successfully. You can access SharePoint Designer 2013 and under workflows options you will have SharePoint 2013 Workflow option available to make Workflows for SharePoint 2013.

Hope this will work for you folks.