diff --git a/recv_server.py b/recv_server.py
index 7d9d8a8..6a59c55 100644
--- a/recv_server.py
+++ b/recv_server.py
@@ -1,18 +1,45 @@
 
-import socket
+import socket, zlib
 
 HOST = "127.0.0.1"  # Standard loopback interface address (localhost)
 PORT = 2000  # Port to listen on (non-privileged ports are > 1023)
 
+def calculate_crc(data):
+    # Calculate the CRC32 checksum of the data
+    crc = zlib.crc32(data)
+    # Convert the CRC32 value to a 4-byte big-endian byte array
+    crc_bytes = crc.to_bytes(4, byteorder='big')
+    return crc_bytes
+
 with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
     s.bind((HOST, PORT))
     s.listen()
     while True:
-        conn, addr = s.accept()
-        with conn:
-            print(f"Connected by {addr}")
-            while True:
-                data = conn.recv(1024)
-                if not data:
-                    break
-                print(f'{data.hex()} [{len(data)}]')
\ No newline at end of file
+        try:
+            conn, addr = s.accept()
+            with conn:
+                print(f"Connected by {addr}")
+                while True:
+                    data = conn.recv(1024)
+                    if not data:
+                        break
+                    print(f'RECV: {data.hex()} [{len(data)}]')
+                    if data[0x11] == 0x01:
+                        pckt = bytearray([0x01])
+                        pckt.extend([0x00, 0x00, 0x00, 0x00]) # src
+                        pckt.extend([0x00, 0x00, 0x00, 0xFF]) # dest
+                        pckt.extend([0x00, 0x00, 0x00, 0x00]) # packet_id
+                        pckt.extend(data[0x09:0x0D]) # reply_to
+                        pckt.extend([0x01]) # command
+                        pckt.extend([0x00, 0x04]) # data_length
+                        pckt.extend([0x00, 0x00, 0x00, 0xFF])
+
+                        # Calculate CRC for the received data
+                        crc = calculate_crc(pckt)
+                        # Append the CRC value to the data
+                        data_with_crc = pckt + crc
+                        # Send the modified data (with CRC) back to the client
+                        conn.sendall(data_with_crc)
+                        print(f'SEND: {data_with_crc.hex()} [{len(data_with_crc)}]')
+        except:
+            s.close()
\ No newline at end of file