curl Error Messages

Transfer data with URLs.All curl pages

curl: (28) Operation timed out after N milliseconds with 0 bytes receivedcurl: (28) Operation timed out means --max-time or --connect-timeout ran out first: a slow or hung server, a firewall that drops packets, or a slow proxy.
curl: (52) Empty reply from servercurl: (52) Empty reply from server means the server accepted the connection and closed it without any HTTP response: a crash, a proxy or HTTP sent to TLS.
curl: (6) Could not resolve hostcurl: (6) Could not resolve host means the host name in the URL did not resolve to an IP: a typo, bad quoting, no DNS, a VPN or proxy issue. How to check each.
curl: (7) Failed to connect to localhost port 8080: Connection refusedcurl: (7) Failed to connect means nothing accepted the TCP connection on that host and port: the server is down, on another port or bound to another address.