解决ADOConnection1连接数据库假死

1用ADOConnection1连接数据库时，如果数据库不存在都会等待很久，甚至会出现假死情况。要避免这种情况可以用扫描一下SQL的端口1433是否开放。扫描代码如下

function ScanTCPPort(ipstr: string; Port: DWORD): Boolean;
var
  option: DWORD;
  TcpSock: TSocket;
  InAddr: TSockAddrIn;
  IP: DWORD;
begin
  result := False;

  //convert IP string to ulong
  IP := ntohl(inet_addr(PChar(ipstr)));
  if IP = INADDR_NONE then //invalid IP address!
    exit;

  // Create/open a socket (stream, not datagram)
  TcpSock := socket(AF_INET, SOCK_STREAM, 0);
  if TcpSock = INVALID_SOCKET then //socket error
    exit;

  try
    // Set socket options
    option := 0;
    setsockopt(TcpSock, SOL_SOCKET, SO_KEEPALIVE, @option, sizeof(option));
    option := 1;
    setsockopt(TcpSock, SOL_SOCKET, SO_DONTLINGER, @option, sizeof(option));

    //if winsock 1.1, including the next sentence, otherwise, skip it.
    setsockopt(TcpSock, IPPROTO_TCP, TCP_NODELAY, @option, sizeof(option));

    //Initialize address structure
    ZeroMemory(@InAddr, sizeof(InAddr));
    InAddr.sin_family := AF_INET;
    InAddr.sin_addr.S_addr := ntohl(IP);
    InAddr.sin_port := htons(Port);
    //Try to connect
    Result := connect(TcpSock, InAddr, sizeof(InAddr)) = 0;
  finally
    //Close the socket
    closesocket(TcpSock);
  end;
end;