Socket中如何设置连接超时（转）

http://tangfeng.iteye.com/blog/795497

Socket中可以使用select设置连接超时，需要先将socket设置为非锁定模式，这样，在connect时，才会立马跳过，同时，通常也会产生一个WSAEWOULDBLOCK错误，这个错误没关系。再执行select则是真正的超时。 

WSADATA wsd;
SOCKET cClient;
int ret;
struct sockaddr_in server;
hostent *host = NULL;

if (WSAStartup(MAKEWORD(2,0), &wsd))
{
    return 0;
}
cClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (cClient == INVALID_SOCKET)
{
    return 0;
}

// set Recv and Send time out
DWORD TimeOut = 6000; // 设置发送超时6秒
if (::setsockopt(cClient, SOL_SOCKET, SO_SNDTIMEO, (char *)&TimeOut, sizeof(TimeOut)) == SOCKET_ERROR)
{
    return 0;
}

TimeOut = 6000; // 设置接收超时6秒
if (::setsockopt(cClient, SOL_SOCKET, SO_RCVTIMEO, (char *)&TimeOut, sizeof(TimeOut)) == SOCKET_ERROR)
{
    return 0;
}

// 设置非阻塞方式连接
unsigned long ul = 1;
ret = ioctlsocket(cClient, FIONBIO, (unsigned long*)&ul);
if (ret == SOCKET_ERROR)
    return 0;

// 连接
server.sin_family = AF_INET;
server.sin_port = htons(25);
server.sin_addr.s_addr = inet_addr((LPCSTR)pSmtp);
if (server.sin_addr.s_addr == INADDR_NONE)
    return 0;

connect(cClient, (const struct sockaddr*)&server, sizeof(server));

// select 模型，即设置超时
struct timeval timeout ;
fd_set r;
FD_ZERO(&r);
FD_SET(cClient, &r);
timeout.tv_sec = 15; // 连接超时15秒
timeout.tv_usec = 0;
ret = select(0, 0, &r, 0, &timeout);
if (ret <= 0)
{
    ::closesocket(cClient);
    return 0;
}

// 一般非锁定模式套接字比较难控制，可以根据实际情况考虑再设回阻塞模式
unsigned long ul1 = 0;
ret = ioctlsocket(cClient, FIONBIO, (unsigned long*)&ul1);
if (ret == SOCKET_ERROR)
{
    ::closesocket(cClient);
    return 0;
}