POST to 127.0.0.1 doesn't work

Followed the link here Using Custom Domains With IIS Express

In Chrome, I can access my web server by both https://localhost:44301 and https://127.0.0.1:44301

But when I tried to send POST strings to this web server, only localhost works, 127.0.0.1 will have "Connection refused" error.

For example, if using curl, the following command can work,

curl.exe -s -d "xxxxx=yyyyy" https://localhost:44301/API/NNN/Register

But the following command won't work,

curl.exe -s -d "xxxxx=yyyyy" http://ift.tt/2owcpfI

Could someone point out what I forget to do? My web server is developed by Visual Studio C# and IIS.

Thanks.