curl Failed to connect to localhost port 80

Since you have a ::1 localhost line in your hosts file, it would seem that curl is attempting to use IPv6 to contact your local web server.

Since the web server is not listening on IPv6, the connection fails.

You could try to use the --ipv4 option to curl, which should force an IPv4 connection when both are available.

If anyone else comes across this and the accepted answer doesn't work (it didn't for me), check to see if you need to specify a port other than 80. In my case, I was running a rails server at localhost:3000 and was just using curl http://localhost, which was hitting port 80.

Changing the command to curl http://localhost:3000 is what worked in my case.

In my case, the file ~/.curlrc had a wrong proxy configured.

I also had problem with refused connection on port 80. I didn't use localhost.

curl --data-binary "@/textfile.txt" "http://www.myserver.com/123.php"

Problem was that I had umlauts äåö in my textfile.txt.