(in-package :trivial-sockets) ;; you're using a part of the interface that the implementation doesn't do (define-condition unsupported (error) ((feature :initarg :feature :reader unsupported-feature))) ;; all-purpose error: host not found, host not responding, ;; no service on that port, etc (define-condition socket-error (error) ((nested-error :initarg :nested-error :reader socket-nested-error)))