udnspkt: Add example.

udnspkt/example_resolve.py

@@ -0,0 +1,29 @@
+import uio
+import usocket
+
+import udnspkt
+
+
+s = usocket.socket(usocket.AF_INET, usocket.SOCK_DGRAM)
+dns_addr = usocket.getaddrinfo("127.0.0.1", 53)[0][-1]
+
+
+def resolve(domain, is_ipv6):
+    buf = uio.BytesIO(48)
+    udnspkt.make_req(buf, "google.com", is_ipv6)
+    v = buf.getvalue()
+    print("query: ", v)
+    s.sendto(v, dns_addr)
+
+    resp = s.recv(1024)
+    print("resp:", resp)
+    buf = uio.BytesIO(resp)
+
+    addr = udnspkt.parse_resp(buf, is_ipv6)
+    print("bin addr:", addr)
+    print("addr:", usocket.inet_ntop(usocket.AF_INET6 if is_ipv6 else usocket.AF_INET, addr))
+
+
+resolve("google.com", False)
+print()
+resolve("google.com", True)