Is there a reason you need to use the ip address for local host rather than the string name"localhost" if you are able to play your game in the browser?
In order to help you it will be good to know what your end goal is in this instance.
thank you!
My goal is starting the HTML5LaunchHelper.exe of my game on one computer, and playing it on a browser of another computer.
127.0.0.1 is only a simple testing for ip address.
The HTML5LaunchHelper.exe was intended for testing on your own machine and creates a local host that can only be accessed by the machine launching the helper.
If you want to test networking with other computers you will have to create the network functionality either in code or blueprint and run the project. Here is a link for Online Session Nodes.