Second SSH/MySQL connection uses existing tunnel from first connection

[ansgarbecker]

Description

Both sessions are set to use the same local port (3307 in my case).

Second connection to a testing server shows databases from the first one, so I'm reusing the first tunnel.

Probably because apphelpers.PortOpen(3307) fails?
Probably only on Windows?

In my case the command returns the expected string :3307 and should then use a different port:

$ netstat -na -p TCP
...
TCP    127.0.0.1:3307         0.0.0.0:0              ABHÖREN

HeidiSQL version

12.14.1.1

Database server version

Reproduction recipe

Open one SSH tunnel session, then another one. Watch out for the databases displayed in the second connection.

Error/Backtrace

[ansgarbecker]

A probable better approach than using netcat on Linux and netstat on Windows is a cross-platformic use of BSD sockets API that FPC exposes in the Sockets (and WinSock-compatible) RTL units.
And let's rename the confusing name PortOpen to IsPortFree.

uses
  Sockets;  // no BaseUnix

function IsPortFree(APort: Word; const AIP: string = '127.0.0.1'): Boolean;
var
  s: LongInt;
  addr: TInetSockAddr;
begin
  Result := False;

  s := fpSocket(AF_INET, SOCK_STREAM, 0);
  if s < 0 then
    Exit;

  try
    FillChar(addr, SizeOf(addr), 0);
    addr.sin_family := AF_INET;
    addr.sin_port   := htons(APort);
    addr.sin_addr   := StrToNetAddr(AIP);

    if fpBind(s, @addr, SizeOf(addr)) = 0 then
      Result := True
    else
      Result := False;
  finally
    fpClose(s);  // from Sockets, works on all supported OSes
  end;
end;

[ansgarbecker]

Works now, on Windows and Linux, thanks to the new cross-compilic IsPortOpen function