Delphi ActiveX

Upgrade a Plain TCP Connection to TLS

Demonstrates Socket.ConvertToSsl, which upgrades an already-connected plain TCP socket to TLS by performing a client-side TLS handshake over the existing connection.

Background. This supports STARTTLS-style upgrades, where a protocol begins in plaintext and switches to TLS at a defined point. Perform the protocol-specific negotiation first, then call ConvertToSsl.

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var
success: Integer;
socket: TChilkatSocket;
bTls: Integer;
maxWaitMs: Integer;

begin
success := 0;

socket := TChilkatSocket.Create(Self);

//  Connect as plain TCP (no TLS yet).
bTls := 0;
maxWaitMs := 5000;
success := socket.Connect('example.com',5000,bTls,maxWaitMs);
if (success = 0) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;

//  At the point where the application protocol permits a STARTTLS-style upgrade, perform any required
//  negotiation, then upgrade the existing connection to TLS with a client-side handshake.
success := socket.ConvertToSsl();
if (success = 0) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add('Connection upgraded to TLS.');