Getting Error: "Unable to connect to the remote server" when using TokenHelper.GetAppOnlyAccessToken in Provider Hosted App

Hi Team,

Getting Error: "Unable to connect to the remote server" when using TokenHelper.GetAppOnlyAccessToken in Provider Hosted App.

In my scenario I am creating Provider Hosted App for an On-Premise SharePoint Server. There I want to create Site collection on a Web Application using Client Object Model. For Site Collection process i am using below attached code:

Private void CreateSiteCollection(SiteTemplateEntity selectedConfig)

{

string webUrl ="";

Uri targetUri =newUri(TENANT_ADMIN_URL);

var token =TokenHelper.GetAppOnlyAccessToken(SHAREPOINT_PID, targetUri.Authority,TokenHelper.GetRealmFromTargetUrl(targetUri)).AccessToken;

using (var clientContext =TokenHelper.GetClientContextWithAccessToken(targetUri.ToString(), token))

{

var tenant =newTenant(clientContext);

webUrl =String.Format("{0}{1}", selectedConfig.BasePath, txtWebName.Text);

var properties =newSiteCreationProperties()

{

Url = webUrl,

Owner =“domain\userid”,

Title ="ABC",

Template = selectedConfig.SiteTemplate,

StorageMaximumLevel = 100,

UserCodeMaximumLevel = 300

};

SpoOperation op = tenant.CreateSite(properties);

clientContext.Load(tenant);

clientContext.Load(op, i => i.IsComplete);

clientContext.ExecuteQuery();

while (!op.IsComplete)

{

System.Threading.

Thread.Sleep(30000);

op.RefreshLoad();

clientContext.ExecuteQuery();

}

}

}

Call to GetAppOnlyaccessToken method throws attached issue.

Please suggest how to resolve this issue.

Thanks

Prabhat