diff --git a/bootloader.py b/bootloader.py
index 8e96ced..098a47c 100644
--- a/bootloader.py
+++ b/bootloader.py
@@ -19,9 +19,11 @@
 # CAN command message IDs.
 ERASE_SECTOR_CAN_ID_LOWBITS = 0x4
 ERASE_SECTOR_COMPLETE_CAN_ID_LOWBITS = 0x5
-PROGRAM_CAN_ID_LOWBITS = 0x6
+NAK_ID = 0x6
 VERIFY_CAN_ID_LOWBITS = 0x7
 APP_VALIDITY_CAN_ID_LOWBITS = 0x8
+APP_START_PROGRAM_ID = 0xA # this is BOARD LOW BIT + 0xA -- we have until boot_id_range_start + 0xFFFFFF
+FINAL_PROGRAM_ID = 0xFFFFFF 
 
 # Verify response options.
 # Keep in sync with:
@@ -32,7 +34,7 @@
 
 # The minimum amount of data the microcontroller can program at a time.
 MIN_PROG_SIZE_BYTES = 32
-
+NAK_TIMEOUT = 0.1 
 
 class Bootloader:
     bus: can.Bus
@@ -54,7 +56,7 @@ def __init__(
         self.board: boards.Board = board
         self.timeout: int = timeout
         self.ui_callback: Callable = ui_callback
-
+        self.dropped_packets = set()
     def goto_bootloader(self) -> bool:
         """
         Pushes all boards to bootloader mode.
@@ -182,30 +184,89 @@ def program(self) -> None:
         Program the binary into flash. There is no CAN handshake here to reduce
         latency during programming. Also, the bootloader will verify the app's code is valid
         by computing a checksum.
-
         """
-        for i, address in enumerate(
-            range(self.ih.minaddr(), self.ih.minaddr() + self.size_bytes(), 8)
-        ):
-            if self.ui_callback and i % 128 == 0:
-                self.ui_callback("Programming data", self.size_bytes(), i * 8)
 
-            data = [self.ih[address + i] for i in range(0, 8)]
+        self.__transmission_address = self.ih.minaddr()
+        self.__transmission_id = self.board.boot_id_range_start | APP_START_PROGRAM_ID
+        self.__index = 0
+
+        def _validator(msg: can.Message):
+            # Ignore all known status messages
+            print(f"Can ID that come through {msg.arbitration_id}\n")
+            if msg.arbitration_id ==  (self.board.boot_id_range_start | NAK_ID):
+                dropped_packet_address = int.from_bytes(msg.data, "little")
+                self.__transmission_address = (dropped_packet_address // 8) * 8
+                self.__index = dropped_packet_address % 8
+                self.__transmission_id = self.board.boot_id_range_start | APP_START_PROGRAM_ID
+                return False
+            else:
+                return True 
+
+        while self.__transmission_address < self.ih.minaddr() + self.size_bytes():
+
+            if self.ui_callback and self.__index % 128 == 0:
+                self.ui_callback("Programming data", self.size_bytes(), self.__index * 8)
+                self.__index += 1
+            
+            data = [self.ih[self.__transmission_address + i] for i in range(0, 8)]
 
             success = False
-            while not success:
-                try:
-                    self.bus.send(
-                        can.Message(
-                            arbitration_id=self.board.boot_id_range_start
-                            | PROGRAM_CAN_ID_LOWBITS,
-                            data=data,
-                            is_extended_id=True,
+            if(self.__transmission_id <= (self.board.boot_id_range_start | FINAL_PROGRAM_ID)):
+                while not success:
+                    try:
+                        self.bus.send(
+                            can.Message(
+                                arbitration_id=self.__transmission_id,
+                                data=data,
+                                is_extended_id=True,
+                            )
                         )
-                    )
-                    success = True
-                except can.interfaces.vector.exceptions.VectorOperationError:
-                    pass
+                        success = True
+                    except can.interfaces.vector.exceptions.VectorOperationError:
+                        pass
+
+                nak = ~self._await_can_msg(_validator, timeout=NAK_TIMEOUT)
+
+                if nak == False:
+                    print(f"WE LIT!!!!! PACKET {self.__transmission_address} recieved\n")
+                    self.__transmission_address += 8
+                elif nak == True: 
+                    print(f"PACKET DROPPED, Re-transmission starting at address {self.__transmission_address}\n")
+                    print(f"PACKET DROPPED, Re-transmission starting at index {self.__index}\n")
+                else:
+                    print("TIMEOUT\n")
+
+
+        # for i, address in enumerate(
+        #     range(self.ih.minaddr(), self.ih.minaddr() + self.size_bytes(), 8)
+        # ):
+        #     self.__transmission_address = address #use an internal pointer
+
+        #     if self.ui_callback and i % 128 == 0:
+        #         self.ui_callback("Programming data", self.size_bytes(), i * 8)
+        #     data = [self.ih[address + i] for i in range(0, 8)]
+
+        #     success = False
+        #     if(self.__transmission_id <= (self.board.boot_id_range_start | FINAL_PROGRAM_ID)):
+        #         while not success:
+        #             try:
+        #                 self.bus.send(
+        #                     can.Message(
+        #                         arbitration_id=self.__transmission_id,
+        #                         data=data,
+        #                         is_extended_id=True,
+        #                     )
+        #                 )
+        #                 success = True
+        #             except can.interfaces.vector.exceptions.VectorOperationError:
+        #                 pass
+        #     else:
+        #         print(f"RAN OUT OF BOARD IDS, current can ID {self.__transmission_id}")
+            
+
+            # Empirically, this tiny delay between messages seems to improve reliability.
+            time.sleep(0.0005)
+
         if self.ui_callback:
             self.ui_callback("Programming data", self.size_bytes(), self.size_bytes())
 
@@ -251,7 +312,6 @@ def update(self) -> None:
         Run the update procedure for this bootloader.
 
         """
-
         def _intersect(a_min, a_max, b_min, b_max):
             """1-D intersection to check if an app's hex and a flash sector share any addresses."""
             return a_max >= b_min and b_max >= a_min
@@ -368,4 +428,4 @@ def size_bytes(self) -> int:
         return int(
             math.ceil((self.ih.maxaddr() - self.ih.minaddr()) / MIN_PROG_SIZE_BYTES)
             * MIN_PROG_SIZE_BYTES
-        )
+        )
\ No newline at end of file