I think we need a little more information based on your question.
I'm going to guess you have a web server running to accept requests? I currently don't, and Safari won't connect to 127.0.0.1, because it "Couldn't find 127.0.0.1" - even though I can ping it just fine.
So first, you need to have something running. Secondly, have you tried connecting to testing.localhost with Safari, just incase the two entries are confusing Safari (this is entirely possible).
When you say "applications can connect as normal" with Chrome and Firefox, what are you seeing? The web page you're expecting to see? A different error?
Edit
I downloaded and installed MAMP, and I could not reproduce this error.
Some forum threads suggest IPv6 resolution is causing this issue. I would be inclined to turn off IPv6 and remove the entry from the hosts file (temporarily just for testing)
- Apple Menu > System Preferences
- Network
- Select your Network Connection > Advanced
- Configure IPv6 > Off
Apply, restart, and see how it goes.
Check your hosts file - this is where host names are resolved in first place.
Normally, you should find this line there:
127.0.0.1 localhost
If not, add this line, save it and then test again, whether it works.
The hosts file can be found at:
%WINDIR%\system32\drivers\etc
You can edit this file with any text editor (e.g. notepad).
Best Answer
127 is the last network number in a class A network with a subnet mask of
255.0.0.0
.127.0.0.1
is the first assignable address in the subnet.127.0.0.0
cannot be used because that would be the wire number. But using any other numbers for the host portion should work fine and revert to using127.0.0.1
. You can try it yourself by pinging127.1.1.1
if you'd like. Why they waited until the last network number to implement this? I don't think it's documented.