logn int BigData = 128.
void *p = (void *)&BigData;

char ch_data = *p;
short int m_data = *p;
int mm_data = *p;
long int l_data = *p;

short int Data = 232443;
void *p = (void *)&Data;

long int b_data = *p;
b_data &= 0x0000FFFF;

typedef struct TCP_Head_tag {
    uint16_t SRC_Port;         // Порт отправителя
    uint16_t DST_Port;         // Порт получателя
    uint32_t SeqNum;           // Sequence Number
    uint32_t AckNum;           // Acknowledgment Number
    union {
        struct {
            uint16_t FIN        : 1;    // No more data from sender
            uint16_t SYN        : 1;    // Synchronize sequence numbers
            uint16_t RST        : 1;    // Reset the connection
            uint16_t PSH        : 1;    // Push Function
            uint16_t ACK        : 1;    // Acknowledgment field significant
            uint16_t URG        : 1;    // Urgent Pointer field significant
            uint16_t Res1       : 6;    //: 4;    // Reserved - 0
            uint16_t DOff       : 4;    // Data Offset - 5
        };
        uint16_t L1;
    };
/*
    union {
        struct {
            uint16_t DOff       : 4;    // Data Offset - 5
            uint16_t Res1       : 6;    //: 4;    // Reserved - 0
            uint16_t URG        : 1;    // Urgent Pointer field significant
            uint16_t ACK        : 1;    // Acknowledgment field significant
            uint16_t PSH        : 1;    // Push Function
            uint16_t RST        : 1;    // Reset the connection
            uint16_t SYN        : 1;    // Synchronize sequence numbers
            uint16_t FIN        : 1;    // No more data from sender
        };
        uint16_t L1;
    };
*/
    uint16_t Window;              // Window - -
    uint16_t Checksum;            // Checksum
    uint16_t UrgPoint;            // Urgent Pointer
} TCP_Head;

#pragma push
#pragma pack(1)
……………………
#pragma pop

#define LITTLE_ENDIAN_MODE 1

#ifdef LITTLE_ENDIAN_MODE
  swap
#elseif
  not_swap
#endif

#define __ORDER_LITTLE_ENDIAN__ 1234
#define __ORDER_BIG_ENDIAN__ 4321
#define __ORDER_PDP_ENDIAN__ 3412
#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__

#define FLAG_1     1

........................
Flags |= (1 << FLAG_1);

   union {
        struct {
            uint16_t FIN        : 1;    // No more data from sender
            uint16_t SYN        : 1;    // Synchronize sequence numbers
            uint16_t RST        : 1;    // Reset the connection
            uint16_t PSH        : 1;    // Push Function
            uint16_t ACK        : 1;    // Acknowledgment field significant
            uint16_t URG        : 1;    // Urgent Pointer field significant
            uint16_t Res1       : 6;    //: 4;    // Reserved - 0
            uint16_t DOff       : 4;    // Data Offset - 5
        };
        uint16_t L1;
    };

L1 |= (1 << 1)