(in-package :trivial-sockets) (defun resolve-hostname (name)   (cond    ((eql name :any)  #(0 0 0 0))    ((typep name '(vector * 4)) name)    (t (car (sb-bsd-sockets:host-ent-addresses             (sb-bsd-sockets:get-host-by-name name)))))) (defun open-stream (peer-host peer-port                               &key (local-host :any) (local-port 0)                               (external-format :default)                               (element-type 'character)                               (protocol :tcp))   (unless (eql external-format :default)     (error 'unsupported :feature :external-format))   (handler-bind ((sb-bsd-sockets:socket-error                   (lambda (c) (error 'socket-error :nested-error c)))                  (sb-bsd-sockets:name-service-error                   (lambda (c) (error 'socket-error :nested-error c))))     (let ((s (make-instance 'sb-bsd-sockets:inet-socket                             :type :stream                             :protocol protocol))           (me (resolve-hostname local-host)))       (unless (and (equal me #(0 0 0 0)) (eql local-port 0))         (sb-bsd-sockets:socket-bind s me local-port))       (sb-bsd-sockets:socket-connect        s (resolve-hostname peer-host) peer-port)       (sb-bsd-sockets:socket-make-stream  s :input t :output t                                           :element-type element-type                                           :buffering :full)))) (defun open-server (&key (host :any) (port 0)                          (reuse-address t)                          (backlog 1)                          (protocol :tcp))   "Returns a SERVER object and the port that was bound, as multiple values"   (let ((sock (make-instance 'sb-bsd-sockets:inet-socket                              :type :stream                              :protocol protocol)))     (when reuse-address       (setf (sb-bsd-sockets:sockopt-reuse-address sock) t))     (sb-bsd-sockets:socket-bind  sock (resolve-hostname host) port)     (sb-bsd-sockets:socket-listen sock backlog)     (multiple-value-bind (h p) (sb-bsd-sockets:socket-name sock)       (declare (ignore h))       (values sock p)))) (defun close-server (server)   (sb-bsd-sockets:socket-close server)) (defun accept-connection (socket                           &key                           (external-format :default)                           (element-type 'character))   (unless (eql external-format :default)     (error 'unsupported :feature :external-format))   (let ((s (sb-bsd-sockets:socket-accept socket)))     (sb-bsd-sockets:socket-make-stream s                                        :input t :output t                                        :element-type element-type                                        :buffering :full)))