My SQL server discovery on LAN by listening port (Inno Setup)

Question

I need to search for an IP address with Listening Port to look up for others PC on LAN (try to discovery MySQL server) and get the results I

Answer 1

To check if a server is listening on a port, you can use Winsock OLE control:

type
  TSocketState =
    (sckClosed, sckOpen, sckListening, sckConnectionPending, sckResolvingHost,
     sckHostResolved, sckConnecting, sckConnected, sckClosing, sckError);

type
  TMsg = record
    hwnd: HWND;
    message: UINT;
    wParam: Longint;
    lParam: Longint;
    time: DWORD;
    pt: TPoint;
  end;

const
  PM_REMOVE = 1;

function PeekMessage(var lpMsg: TMsg; hWnd: HWND; wMsgFilterMin, wMsgFilterMax,
  wRemoveMsg: UINT): BOOL; external 'PeekMessageA@user32.dll stdcall';
function TranslateMessage(const lpMsg: TMsg): BOOL;
  external 'TranslateMessage@user32.dll stdcall';
function DispatchMessage(const lpMsg: TMsg): Longint;
  external 'DispatchMessageA@user32.dll stdcall';

procedure AppProcessMessage;
var
  Msg: TMsg;
begin
  while PeekMessage(Msg, 0, 0, 0, PM_REMOVE) do
  begin
    TranslateMessage(Msg);
    DispatchMessage(Msg);
  end;
end;

function CheckPort(Host: string; Port: Integer): Boolean;
var
  Socket: Variant;
begin
  Socket := CreateOleObject('MSWinsock.Winsock');
  Socket.RemoteHost := Host;
  Socket.RemotePort := Port;
  Socket.Connect;

  { Winsock requires message pumping }
  while not (Socket.State in [sckConnected, sckError]) do 
  begin
    AppProcessMessage;
  end;

  Result := (Socket.State = sckConnected);

  if Result then
  begin
    Log(Format('Port %d on %s is open', [Port, Host]));
  end
    else
  begin
    Log(Format('Port %d on %s is NOT open', [Port, Host]));
  end;
  Socket.Close;
end;

Note that the Winsock control requires message queue pumping. So you may need to disable wizard before running the check, to prevent user from messing with the form.

---

Credits: The AppProcessMessage comes from How to execute 7zip without blocking the InnoSetup UI?

Answer 2

My go-to for checking open ports is the Nmap program.

An example command to probe address 192.168.200.133 on TCP port 3306 would be this:

nmap -sT -sV -Pn -n -p 3306 192.168.200.133

You can also scan an entire subnet by giving a CIDR range instead of an IP. As example, to scan for MySQL instances (TCP port 3306) on 192.168.200.1 - 192.168.200.254, you could do:

nmap -sT -sV -Pn -n -p 3306 192.168.200.0/24

^^ These examples were taken straight from https://securityblog.gr/1549/discover-open-mysql-ports/

Nmap is very commonly used on Unix/Linux, but has been ported to Windows, first in year 2000, currently supported on Win 7 or newer (including Server 2008). See https://nmap.org/book/inst-windows.html