Hi Saurabh,
This is https based URL so you need to register for this first. Getting started with the SAP Netweaver Gateway Service Consumption System
Note: Once you get credentials for accessing SAP gateway demo system and try to hit https://sapes1.sapdevcenter.com/sap/bc/srt/rfc/sap/z_sepm_gws_stock_get/520/service/binding , you will a login failed error. because it accepts some inputs to be passed.
Rgrds,
JK
PS: If possible, you should try with this tutorial. It is really nice and will give more understanding about IG.