www.pudn.com > OverlappedServer.rar > comm.cpp

////////////////////////////////////////////////// 
// comm.cpp文件 
 
 
#include  
#include  
#include "Ws2tcpip.h" 
 
#include "comm.h" 
 
 
USHORT checksum(USHORT* buff, int size) 
{ 
	unsigned long cksum = 0; 
	while(size>1) 
	{ 
		cksum += *buff++; 
		size -= sizeof(USHORT); 
	} 
	// 是奇数 
	if(size) 
	{ 
		cksum += *(UCHAR*)buff; 
	} 
	// 将32位的chsum高16位和低16位相加，然后取反 
	cksum = (cksum >> 16) + (cksum & 0xffff); 
	cksum += (cksum >> 16);			// ???	 
	return (USHORT)(~cksum); 
} 
 
BOOL SetTTL(SOCKET s, int nValue) 
{ 
	int ret = ::setsockopt(s, IPPROTO_IP, IP_TTL, (char*)&nValue, sizeof(nValue)); 
	return ret != SOCKET_ERROR; 
} 
 
BOOL SetTimeout(SOCKET s, int nTime, BOOL bRecv) 
{ 
	int ret = ::setsockopt(s, SOL_SOCKET,  
		bRecv ? SO_RCVTIMEO : SO_SNDTIMEO, (char*)&nTime, sizeof(nTime)); 
	return ret != SOCKET_ERROR; 
}