The --help output for curl lists a --resolve option, which states

--resolve <host:port:address> Force resolve of HOST:PORT to ADDRESS

I'm not having any luck getting it to work though. The basic command I'm trying to run is

curl --resolve foo.example.com:443:localhost https://foo.example.com:443/

and I keep getting the response Couldn't resolve host 'foo.example.com'. I want do do this because I'm testing a certificate for foo.example.com, but I'm not testing it on the actual server. Instead, I'm testing it on a dummy machine. I know that I can edit /etc/hosts so that foo.example.com resolves to localhost, but this curl approach seems like it would be the "correct" way to go, if I could make it work.

Does anybody see what I'm doing wrong here?


It appears that the address needs to be a numeric IP address, not a hostname.

Try this:

curl --resolve foo.example.com:443: https://foo.example.com:443/
  • This makes sense because in the DNS world, resolve means "get an IP address from a name". – vastlysuperiorman May 16 at 21:44

Some additional help in troubleshooting:

Ensure you're listening the right port for the protocol: http=80; https=443 & etc

Also curl -v will give the HEADER information for the response server which can be helpful.

curl -v --resolve foo.example.com:443: https://foo.example.com:443/
## The client request headers prepended by >
> OPTIONS /v1/..
> HOSTS foo.example.com
## The server response prepended by <
< HTTP/1.1 501 Not Implemented
## The html returned
<H1>Unsupported Request</H1>

Basically in this case the OPTIONS HTTP method was not implemented at the edge server for the CDN.

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