¹ A whois query is considered to have failed in any of the following cases:

• query timed out
• query returned no output
• query returned a TCP/IP error, such as "connection refused"
• query returned text output with no information on requested domain
• query to registrar indicated that the domain was not found in their database even though the registry points to that registrar
• query to registrar returned output from registry database instead of its own

² Whois services run on TCP/IP port 43, often on a server that can be accessed via the host/service name "whois" under the domain name for the registration service (ex: whois.registrar.com). The actual host name for a registrar's whois query can sometimes be found in the output from a registry whois query.