The path should be in the request line (the first line) after the method name (GET in this case). Currently you tell nc
to look up the hostname www.iana.org/domains/reserved
which will fail. Also the "Host" header should not include the path, only the hostname.
This should work:
printf 'GET /domains/reserved HTTP/1.1\r\nHost: www.iana.org\r\nConnection: close\r\n\r\n' | nc www.iana.org 80