Pascal (Lazarus/Delphi)

Socket Receive String Until Specific Byte Value is Received

Demonstrates the Chilkat Socket ReceiveStringUntilByte method. 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;
  sock: TSocket;
  useTls: Boolean;
  port: Integer;
  maxWaitMs: Integer;
  lookForByte: Integer;
  s1: string;
  s2: string;

begin
  success := False;

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

  sock := TSocket.Create;

  //  --------------------------------------------------------------------
  //  This example uses the public TCP echo service at https://tcpbin.com/
  //  --------------------------------------------------------------------

  useTls := False;
  port := 4242;
  maxWaitMs := 5000;
  success := sock.Connect('tcpbin.com',port,useTls,maxWaitMs);
  if (success = False) then
    begin
      WriteLn(sock.LastErrorText);
      Exit;
    end;

  //  Wait a max of 2 seconds for a response..
  sock.MaxReadIdleMs := 2000;

  //  Send some strings, each terminated by a 0 byte.
  sock.SendString('This is the 1st string');
  sock.SendByte(0);
  sock.SendString('This is string number 2');
  sock.SendByte(0);

  //  The tcpbin.com echo server only echoes after receiving an LF (linefeed char)
  sock.SendByte(10);

  //  Now let's receive what is echoed back....
  //  Receive each string and the NULL byte.
  //  The call to ReceiveStringUntilByte will receive incoming data until the lookForByte is encountered.
  //  The lookForByte is receive and discarded (it is not returned in the string)
  lookForByte := 0;
  s1 := sock.ReceiveStringUntilByte(lookForByte);
  if (sock.LastMethodSuccess = False) then
    begin
      WriteLn(sock.LastErrorText);
      Exit;
    end;
  WriteLn(s1);

  s2 := sock.ReceiveStringUntilByte(lookForByte);
  if (sock.LastMethodSuccess = False) then
    begin
      WriteLn(sock.LastErrorText);
      Exit;
    end;
  WriteLn(s2);

  //  The echo server will also echo back the final LF
  sock.ReceiveByte(True);
  maxWaitMs := 100;
  sock.Close(100);

  //  Output:
  //  This is the 1st string
  //  This is string number 2


  sock.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.