Index: src/resolver.cr
==================================================================
--- src/resolver.cr
+++ src/resolver.cr
@@ -141,12 +141,13 @@
         end
       end
     end
 
     def handle_packet(packet : Bytes, sender : Socket::IPAddress) : Nil
+      io = IO::Memory.new(packet, writeable: false)
       begin
-        id = packet[0].to_u16 << 8 | packet[1]
+        id = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
 
         begin
           context = @queries[id]
         rescue KeyError
           return
@@ -154,23 +155,24 @@
 
         return if sender != context.used_ns
 
         @queries.delete(id)
 
-        if packet[2] & 0x80 == 0 ||                       # QR
-           packet[2] & 0x78 != context.raw_data[2] & 0x78 # Opcode
+        byte = io.read_bytes(UInt8)
+        if byte & 0x80 == 0 ||                       # QR
+           byte & 0x78 != context.raw_data[2] & 0x78 # Opcode
           context.block.call(Error::INVALID_REPLY)
           return
         end
 
-        if packet[2] & 0x02 != 0 # TC
+        if byte & 0x02 != 0 # TC
           # TODO: Switch to TCP
           context.block.call(Error::TRUNCATED)
           return
         end
 
-        case packet[3] & 0x0F # RCODE
+        case io.read_bytes(UInt8) & 0x0F # RCODE
         when 0
           error = nil
           try_next_ns = false
         when 1
           error = Error::SERVER_INVALID_FORMAT
@@ -203,16 +205,14 @@
         if error
           context.block.call(error)
           return
         end
 
-        io = IO::Memory.new(packet[4, packet.size - 4], writeable: false)
         qdcount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
         adcount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
         nscount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
         arcount = io.read_bytes(UInt16, IO::ByteFormat::BigEndian)
-      rescue IndexError
       rescue IO::EOFError
       end
     end
 
     def stop : Nil