Asp.net Development Server suspension problem solved

Yesterday, I suddenly found that I was debugging the Asp.net application.ProgramIE always displays connecting, and the page is not displayed for a long time. After analyzing the cause, I found that Firefox accessed the Asp.net development server, and the page was not displayed for a long time. Is there any problem with Asp.net development server. I couldn't figure out any direct reason, so I searched online and used some keywords such as Asp.net Development Server not working, Asp.net Development Server Long time no response, Asp.net Development Server hang, etc, I found that some information was not helpful, and some said I could just reset the IE options. I tried a lot of methods and it was not solved. Later, we saw that the Asp.net development server can only be accessed using localhost, but it cannot be accessed from other hosts. However, this is the local machine and should be localhost. Trying to adjust the zone of IE in the middle is not solved. Then I suddenly remembered that I could try 127.0.0.1. The localhost does not work. It seems that there is a problem with the localhost domain name. Ping localhost. Sure enough, localhost is mapped to: 1, so c: \ windows \ system32 \ drivers \ etc \ hosts is found:

# Localhost name resolution is handled within DNS itself.
#127.0.0.1 localhost
#: 1 localhost

All these rows are annotated.

Why is the localhost mapped to: 1? I tried to write a line 127.0.0.1 localhost and restarted it. I found that Asp.net development server is normal.

This is related to IPv6, so all IPv6 is disable. There should be no problem.