TCPclient.connected problem in Delphi - Indy

Question

I am having problem with IdTCPclient.connected function from Indy in Delphi. I am using Indy10 and Delphi2010 environment. My problem is every time i check the TCP connection with IdTCPclient.connected, it raises exception with these errors EidSocketError, EidReadTimeOut. Is there any way to disconnect and reconnect the connection? (like reset the connection).

Note: I set TCPClient.ReTimeout:= 30000;

The implemented coding for reset the connection is follow.

if IdTCPclient.connected then
  begin
  IdTCPclient.IOHandler.InputBuffer.Clear;
  IdTCPclient.Disconnect;
  end;
sleep(1000);
try
  IdTCPclient.connect;
  except
    on E: Exception do 
      MessageDlg('Connecting Error: '+E.Message, mtError, [mbOk], 0);
  end;

But some point, i get exception and it couldn't connect at all. I am not sure what i am doing wrong.

Should i do this?

• Disconnect first
• Clear input buffer
• Destroy TCPclient
• Re-create new TCPclient
• And then connect it again

If it is the case, can someone provide me a way how to do it properly?

Also, there is another function to re-connecting the TCP in my coding. It also gives me exception as well. I check the connecting before i send a message to TCP. If there is no connection, i reconnect for five times.

result := IdTCPclient.connected
if not result then
  begin
  for k:=0 to 4 do
    beign
    sleep(1000);
    try
      TCPclient.connect;
      except
        on E: Exception do 
          MessageDlg('Connecting Error: '+E.Message, mtError, [mbOk], 0);
      end
    result := TCPclient.connected;
    if result then break;
    end;

With above two coding, program handles reconnecting and reset the connection pretty well. But some point the program cannot re-connect or reset the connection at all.

• What should i do when i get exception? Should i reconnect from exception?
• How do we build coding to check the connection regularly?
• How do we build coding to to get back the connection when it lost?

Kind regards,

Answer 1

Connected() should not be raising any exceptions at all. If it is, then it is likely a bug. Please provide a stack trace showing that.

The best option is to simply avoid using Connected() whenever possible. When you need to perform an I/O operation, just do so, and let Indy raise an exception if a failure occurs. You can then handle it at that moment, eg:

try
  IdTCPClient.DoSomething...
except
  on E: EIdException do begin
    Reconnect;
  end;
end;

procedure Reconnect;
var
  k: Integer;
begin
  IdTCPClient.Disconnect;
  if IdTCPClient.IOHandler <> nil then
    IdTCPClient.IOHandler.InputBuffer.Clear;

  for k := 0 to 4 do
  begin
    Sleep(1000);
    try
      IdTCPClient.Connect;
      Exit;
    except
      on E: Exception do
      begin
        MessageDlg('Connecting Error: '+E.Message, mtError, [mbOk], 0);
        if k = 4 then
          raise;
      end;
    end;
  end; 
end;

Answer 2

before you connect make sure that the passive Boolean of idftp is false when you need file transfert change it to true with binary file option