非阻塞模式下，建立连接没有调用send()和recv()进行数据交互的情况怎么判断服务端连接主动断开？

通过recv()函数，没有数据时返回-1，服务端断开返回0，通过返回0判断服务端是否断开

unsigned long  u32NonBlock = 1;
if ( ioctlsocket(pDlg->m_s32Socket, FIONBIO, &u32NonBlock) )     // 非阻塞
{
closesocket(pDlg->m_s32Socket);
pDlg->m_s32Socket = -1;
continue;
}


CHAR sTemBuf[2] = {0};
INT s32Ret = recv(pDlg->m_s32Socket,sTemBuf, sizeof(sTemBuf), 0);
if (0 == s32Ret) // 判断服务器是否主动断开 断开返回0
{
closesocket(pDlg->m_s32Socket);
pDlg->m_s32Socket = -1;
}


u32NonBlock = 0;
if ( ioctlsocket(pDlg->m_s32Socket, FIONBIO, &u32NonBlock) )     // 阻塞
{
closesocket(pDlg->m_s32Socket);
pDlg->m_s32Socket = -1;
continue;
}

TCP连接在没有数据交互式判断连接断开