Hi,
This Document will helpful to you:
https://docs.splunk.com/Documentation/MobileApp/2.4.4/Install/Login
Host URL: The URL that identifies the location of your Splunk platform instance. Scheme and port are optional when default ports (8000, 8089, 80, 443) are used on the Splunk server; otherwise, you must enter full host URL including scheme, hostname, and Splunk web port number.