diff --git a/hdlc/client.c b/hdlc/client.c
index a4307af..51b4b0a 100644
--- a/hdlc/client.c
+++ b/hdlc/client.c
@@ -3,6 +3,9 @@
 #include <stdio.h>
 #include <fcntl.h>
 
+#define START_FLAG 0x7E
+#define END_FLAG 0x7E
+
 void init_Client(Client* client, bool test_is_valid, uint8_t address, void* serial_port) {
     client->TEST_IS_VALID = test_is_valid;
     client->address = address;
@@ -34,7 +37,7 @@ void connect(Client* client) {
 
     HDLCFrame frame;
     init_HDLCFrame(&frame, 0, 0, data + 3, 256 - 6);
-    if (validate(client, &frame, data, 256)) {
+    if (validate(data, 256)) {
         return;
     } else {
         // Connection failed
@@ -66,32 +69,28 @@ void receive_data(Client* client, uint8_t* recivedData, int lenRecived) {
     }
 }
 
-bool validate(Client* client, HDLCFrame* frame, uint8_t* received_data, size_t received_length) {
-    uint8_t control = received_data[2];
-    if ((control & 0x01) == 0) {
-        // I-frame
-        printf("i frame\n");
-        uint8_t send_sequence_number = (control >> 1) & 0x07;
-        uint16_t crc = (received_data[received_length - 2] << 8) | received_data[received_length - 3];
-        uint16_t calculated_crc = calculate_fcs(received_data + 1, received_length - 4);
-        if (crc == calculated_crc && send_sequence_number == client->_receive_sequence_number && client->TEST_IS_VALID) {
-            client->_receive_sequence_number++;
-            return true;
-        }
-    } else if ((control & 0x03) == 1) {
-        // S-frame
-        printf("s frame\n");
-        // Handle S-frame
-    } else {
-        // U-frame
-        printf("u frame\n");
-        // Handle U-frame
+#include <stdbool.h>
+
+bool validate(const uint8_t* frame, size_t length) {
+    if (length < 4 || frame[0] != START_FLAG || frame[length - 1] != END_FLAG) {
+        // Invalid frame length or missing start/end flag
+        return false;
     }
-    return false;
+
+    uint16_t received_fcs = (frame[length - 3] << 8) | frame[length - 2];
+    uint16_t calculated_fcs = 0xFFFF;
+
+    for (size_t i = 1; i < length - 3; i++) {
+        uint8_t byte = frame[i];
+        calculated_fcs = (calculated_fcs >> 8) ^ (calculated_fcs << 8) ^ byte;
+        calculated_fcs &= 0xFFFF;
+    }
+
+    return received_fcs == calculated_fcs;
 }
 
 int sendSerialData(const char* port, uint8_t* data, size_t length) {
-    int serial_port = open(port, O_RDWR); // Replace "port" with your serial port device
+    int serial_port = open(port, O_RDWR);
 
     if (serial_port < 0) {
         perror("Error opening the serial port");
diff --git a/hdlc/client.h b/hdlc/client.h
index ca306cb..fb18c71 100644
--- a/hdlc/client.h
+++ b/hdlc/client.h
@@ -1,6 +1,4 @@
-//
-// Created by 79513 on 19.06.2023.
-//
+
 
 #ifndef CLIENT_H
 #define CLIENT_H
@@ -23,7 +21,7 @@ void init_Client(Client* client, bool test_is_valid, uint8_t address, void* seri
 void connect(Client* client);
 void send(Client* client, uint8_t* data, size_t data_length);
 void receive_data(Client* client, uint8_t* recivedData, int lenRecived);
-bool validate(Client* client, HDLCFrame* frame, uint8_t* received_data, size_t received_length);
+bool validate(const uint8_t* frame, size_t length);
 int sendSerialData(const char* port, uint8_t* data, size_t length);
 int receiveSerialData(const char* port, uint8_t* data, int length);