BSD socket 非阻塞模式连接

BSD socket 非阻塞模式连接，适用用各种实现BSD socket的操作系统：windows,  linux, unix, ios, android.

int CNetTcpC::StartConnect(LPCSTR pszIPAddr, UINT nPort){        SOCKADDR_IN ctrl_sin;        UINT sock = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);        ctrl_sin.sin_family = AF_INET;        ctrl_sin.sin_addr.s_addr = inet_addr(m_szSvrIP);        ctrl_sin.sin_port = htons(m_uiSvrPort);        bzero(&(ctrl_sin.sin_zero), 8);           int flag = fcntl(sock, F_GETFL, 0);       fcntl(sock, F_SETFL, flag | O_NONBLOCK);       struct timeval tmout;       tmout.tv_sec = 10;       tmout.tv_usec = 0;       setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, &tmout, sizeof(tmout));       int err = connect(sock, (SOCKADDR*)&ctrl_sin, sizeof(ctrl_sin));       printf("Connect error no is %d:\r",err);           //设置select超时时间间隔          fd_set          fdwrite;           struct timeval  tvSelect;               FD_ZERO(&fdwrite);          FD_SET(sock, &fdwrite);      tvSelect.tv_sec = 10;      tvSelect.tv_usec = 0;          int retval = select(sock + 1,NULL, &fdwrite, NULL, &tvSelect);          printf("select error no is %d:\r",retval);      if ( retval <= 0 )      {         close(sock);         sock = INVALID_SOCKET;         return FALSE;      }          //在connect成功之后，设成阻塞模式      flag = fcntl(sock, F_GETFL,0);      flag &= ~ O_NONBLOCK;      fcntl(sock, F_SETFL, flag);      return TRUE;}