Project kick-off

1 files changed, 48 insertions, 0 deletions

diff --git a/src/client.lisp b/src/client.lisp
new file mode 100644
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+++ b/src/client.lisp
@@ -0,0 +1,48 @@
+(defpackage :cl-mdns/client
+  (:use :cl
+	:cl-mdns/packet)
+  (:local-nicknames (:nb :nibbles)
+                    (:f :fsocket))
+  (:export :lookup)) 
+(in-package :cl-mdns/client)
+
+(defvar *mdns-address* #(224 0 0 251))
+(defvar *mdns-port* 5353)
+
+(defun parse-ipv4-response (packet)
+  "Extracts the first IPv4 address found in a DNS response packet."
+  (let* ((qdcount (+ (ash (aref packet 4) 8) (aref packet 5)))
+         (ancount (+ (ash (aref packet 6) 8) (aref packet 7)))
+         (pos 12)) ; Start after header
+    
+    ;; Skip Question section
+    (loop repeat qdcount do
+      (loop while (not (zerop (aref packet pos))) 
+            do (incf pos (1+ (aref packet pos))))
+      (incf pos 5)) ; Skip null byte + Type(2) + Class(2)
+      
+    ;; Parse Answer section
+    (if (> ancount 0)
+        (let ((type (+ (ash (aref packet (+ pos 2)) 8) (aref packet (+ pos 3))))
+              ;(rdlen (+ (ash (aref packet (+ pos 10)) 8) (aref packet (+ pos 11))))
+              )
+          ;; If Type is 1 (A record), return the next 4 bytes as an IP string
+          (if (= type 1)
+              (format nil "~D.~D.~D.~D" 
+                      (aref packet (+ pos 12)) (aref packet (+ pos 13))
+                      (aref packet (+ pos 14)) (aref packet (+ pos 15)))
+              "Non-IPv4 record received"))
+        "No answers found")))
+
+(defun lookup (domain)
+  (let ((fd (f:open-socket :type :datagram))
+        (packet (build-query-packet domain))
+        (buffer (make-array 512 :element-type '(unsigned-byte 8))))
+    (unwind-protect
+         (progn 
+           (f:socket-bind fd (f:make-sockaddr-in))
+           (f:socket-sendto fd packet (f:make-sockaddr-in :addr *mdns-address* :port *mdns-port*))
+           (multiple-value-bind (count raddr) (f:socket-recvfrom fd buffer)
+             (declare (ignore raddr))
+             (parse-ipv4-response (subseq buffer 0 count))))
+      (f:close-socket fd))))