windows下设置socket的connect超时

变相的实现connect的超时，我要讲的就是这个方法，原理上是这样的：
1．建立socket
2．将该socket设置为非阻塞模式
3．调用connect()
4．使用select()检查该socket描述符是否可写（注意，是可写）
5．根据select()返回的结果判断connect()结果
6．将socket设置为阻塞模式（如果你的程序不需要用阻塞模式的，这步就省了，不过一般情况下都是用阻塞模式的，这样也容易管理）

// widonws: 默认设置socket TCP client connect为阻塞模式
void TcpConnect(char* strIP, UINT nPort)
{
struct sockaddr_in serverAddress;
SOCKET hSocket = NULL;

hSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if( hSocket==INVALID_SOCKET)
{
return;
}

memset(&serverAddress, 0, sizeof(serverAddress));
serverAddress.sin_family = AF_INET;
serverAddress.sin_addr.s_addr = inet_addr(strIP);
serverAddress.sin_port = htons((short)nPort);
int iTimeOut = 3000;
setsockopt(hSocket,SOL_SOCKET,SO_RCVTIMEO,(char*)&iTimeOut,sizeof(iTimeOut));
setsockopt(hSocket,SOL_SOCKET,SO_SNDTIMEO,(char*)&iTimeOut,sizeof(iTimeOut));

if( SOCKET_ERROR==connect(hSocket, (sockaddr*)&serverAddress, sizeof(serverAddress)) )
{
closesocket(hSocket);
DWORD gle = WSAGetLastError();

return;
}

char buff[] = "hello";
int sl=::send(hSocket,(char*)buff, sizeof(buff), 0);
if( sl<0 )
{
closesocket(hSocket);
return ;
}
closesocket(hSocket);
}

// widonws: 设置socket TCP client connect非阻塞模式
void SockSelect(char* strIP, UINT nPort)
{
SOCKET/*int*/ sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(sockfd < 0)
{
return;
}
struct sockaddr_in serv_addr;

//以服务器地址填充结构serv_addr
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = inet_addr(strIP);
serv_addr.sin_port = htons(nPort);
int error = -1;
int len = sizeof(int);
timeval tm;
fd_set set;
unsigned long ul = 1;
ioctlsocket(sockfd, FIONBIO, &ul); //设置为非阻塞模式
bool ret = false;
if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
{
tm.tv_sec = 3;
tm.tv_usec = 0;
FD_ZERO(&set);
FD_SET(sockfd, &set);
if( select(sockfd+1, NULL, &set, NULL, &tm) > 0)
{
getsockopt(sockfd, SOL_SOCKET, SO_ERROR, (char *)&error, /*(socklen_t *)*/&len);
if(error == 0)
ret = true;
else
ret = false;
}
else
ret = false;
}
else
ret = true;
ul = 0;
ioctlsocket(sockfd, FIONBIO, &ul); //设置为阻塞模式
if(!ret)
{
closesocket( sockfd );
fprintf(stderr , "Cannot Connect the server!/n");
return;
}

fprintf( stderr , "Connected!/n");

char buff[] = "hello";
int sl=::send(sockfd,(char*)buff, sizeof(buff), 0);

closesocket( sockfd );
}