Pascal (Lazarus/Delphi)

Receive Text until CRLF

Demonstrates receiving text on a socket connection up to and including when an expected CRLF arrives. The example sends an HTTP HEAD request to an HTTP server and then reads the response header using ReceiveToCRLF and ReceiveUntilMatch. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Socket;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  socket: TSocket;
  useTls: Boolean;
  maxWaitMillisec: Integer;
  responseStatusLine: string;
  responseHeaderLine: string;
  remainderOfHeader: string;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  socket := TSocket.Create;

  //  Connect using TLS to www.chilkatsoft.com
  //  We could also use a normal TCP connection also by specifying port 80 with useTls = False.
  useTls := True;
  maxWaitMillisec := 20000;
  success := socket.Connect('www.chilkatsoft.com',443,useTls,maxWaitMillisec);
  if (success <> True) then
    begin
      WriteLn(socket.LastErrorText);
      Exit;
    end;

  //  Tell the socket object that all text is to be sent in the utf-8 encoding,
  //  and the text received is assumed to be utf-8.
  socket.StringCharset := 'utf-8';

  //  Send an HTTP HEAD request:
  success := socket.SendString('HEAD / HTTP/1.1' + #13#10 + 'Host: www.chilkatsoft.com' + #13#10 + #13#10);
  if (success <> True) then
    begin
      WriteLn(socket.LastErrorText);
      Exit;
    end;

  //  Wait a maximum of 4 seconds while no data is forthcoming:
  socket.MaxReadIdleMs := 4000;

  //  To explain MaxReadIdleMs further:  In Chilkat, a max "idle timeout" is the max time to wait
  //  while no additional data arrives on the socket.  Imagine if 10MB of data will be received
  //  where the 1st CRLF occurs at the very end.  As long as the data continues arriving and does not
  //  halt for more than 4000ms, then the ReceiveToCRLF will continue receiving.  It is only after
  //  the connection becomes idle for more than 4000ms that the app will giveup and fail the read.

  //  Get the 1st response line, which should be "HTTP/1.1 200 OK"
  responseStatusLine := socket.ReceiveToCRLF();
  if (socket.LastMethodSuccess <> True) then
    begin
      WriteLn(socket.LastErrorText);
      Exit;
    end;

  WriteLn('StatusLine: ' + responseStatusLine);

  //  Now get the 1st line of the response header:
  responseHeaderLine := socket.ReceiveToCRLF();
  if (socket.LastMethodSuccess <> True) then
    begin
      WriteLn(socket.LastErrorText);
      Exit;
    end;

  WriteLn('HeaderLine: ' + responseHeaderLine);

  //  Now read the remainder of the response header by reading until a double CRLF is seen:
  remainderOfHeader := socket.ReceiveUntilMatch(#13#10 + #13#10);
  if (socket.LastMethodSuccess <> True) then
    begin
      WriteLn(socket.LastErrorText);
      Exit;
    end;

  WriteLn('Remainder: ' + remainderOfHeader);

  //  Close the connection with the server
  //  Wait a max of 20 seconds (20000 millsec)
  success := socket.Close(20000);


  socket.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.