Hàm tính checksum cho gói TCP Code:

- Đầu tiên ta cộng các từ 16 bit trong header: Code:

Hàm tính checksum cho gói TCP Code:

Code:

//--- ---

//Duoc goi moi giay de kiem tra Time out cho cac phien TCP, // giai phong cac phine TCP bi treo

void TCPCheckTimeOut(){ unsigned char i;

for(i=0; i<TCP_MAX_SESSION; i++){ //decrement ttl:

if ((tcpSessionTable[i].sesState != TCP_STATE_CLOSED) && (tcpSessionTable[i].sesState != TCP_STATE_LISTEN)){

if(tcpSessionTable[i].timeOut)

tcpSessionTable[i].timeOut--;

//if socket TTL count is zero, close this socket! if (tcpSessionTable[i].timeOut == 0){ TCPCloseSession(i); } } } }

Hàm tính checksum cho gói TCPCode: Code:

//--- ---

//Tinh checksum cho goi TCP

unsigned int checksum(unsigned char *buffer, unsigned int len, unsigned long csum32)

{

unsigned int res16 = 0x0000; unsigned char data_hi;

unsigned char data_lo; while(len > 1){

data_hi = *buffer++; data_lo = *buffer++;

res16 = (((unsigned int)data_hi << 8) + data_lo); csum32 = csum32 + res16;

len -=2; }

if(len > 0){

data_hi = *buffer;

res16 = (unsigned int)data_hi<<8; csum32 = csum32 + res16;

}

while(csum32>>16)

csum32 = (csum32 & 0xFFFF)+ (csum32 >> 16);

//csum32 = ((csum32 & 0x0000FFFF)+ ((csum32 & 0xFFFF0000) >> 16)); res16 =~(csum32 & 0x0000FFFF);

return (res16); }