The ENOTFOUND exception occurs when a connection cannot be established to a host due to a DNS error. To fix this error, ensure that there are no typos in the domain name and use tools like DNS Checker to confirm successful resolution of the domain. Additionally, when using the http.request() or https.request() methods, make sure that the host value in the options object contains only the domain name or IP address of the server. If the ENOTFOUND error is thrown when connecting to localhost, it may indicate that localhost is missing.