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TCP Client(Indy10) with VPN can not detect disconnect when VPN disconnected!!

Posted on 2006-11-27
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Last Modified: 2010-04-04
I'm use Indy10.

I can not sure TIdTCPClient is buggy or VPN Client is buggy!! The situation is:

My client work in VPN to communicate server!!

My client connect to tcp server(TIdTCPServer)  and read until server sent infinitly!!

When VPN was disconnected, TCP.GetResponse() does not throw exception like EIdDisconnected or EIdConClosedGracefully!!

Is it possible like that?

Someone tell me DON'T read wait infinitly, USE ping/pong client with server periodically!!

Is it good solution to establish valid connection ?

What about set read timeout for TIdTCPClient when TIdTCPClientGetResponse()?


Here is code:

procedure TWaitThread.Execute;
var
  TCP: TIdTCPClient;
  S1, S2: string;
begin
  inherited;

  FAbortEvent.ResetEvent;

  TCP := nil;
  try try
    while not Terminated do
    begin
      if nil = TCP then
      begin
        TCP := TIdTCPClient.Create(nil);
        TCP.ReadTimeout := 0;
        TCP.Host := FHost;
        TCP.Port := FPort;
      end;

      if not Tcp.Connected then
      try
        TCP.Connect;
      except
        FreeAndNil(TCP);
      end;
       
      if (nil <> TCP) and (TCP.Connected) then
      try
        S1 := TCP.Socket.ReadLn; // read welcome response
        TCP.Socket.WriteLn('client ' + FClientData);
        TCP.GetResponse(200); // read wait ok response
        S1 := TCP.LastCmdResult.Text.Text;

        Synchronize(DoReadyToWait);

        while not Terminated and not Application.Terminated do
        begin
          if WAIT_OBJECT_0 = WaitForSingleObject(FAbortEvent.Handle, 10) then
            Exit // Aborted
          else
          begin
            TCP.GetResponse(300); // read wait until received msg infinitly!!!  

            FData := TCP.LastCmdResult.Text.Text;
            Synchronize(DoNotify);
          end;
        end;
      except
        if nil <> TCP then
          FreeAndNil(TCP);
      end;

      Sleep(3000); // wait 3 sec, if disconnected
    end;

  except
  end;
  finally
    if nil <> TCP then
    begin
      if TCP.Connected then TCP.Disconnect;
      FreeAndNil(TCP);
    end;
  end;
end;
0
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Question by:byungho
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5 Comments
 
LVL 19

Accepted Solution

by:
MerijnB earned 125 total points
ID: 18025885
using ping/pong (or keepalives) is always a good idea. This is the only way to make sure the connection is there or not when you don't have to sent actually. It is possible you 'think' you can send data, but it never arrives at the other end.
0
 
LVL 19

Expert Comment

by:MerijnB
ID: 18025892
What about set read timeout for TIdTCPClient when TIdTCPClientGetResponse()?

oops, forgot about this one: this could work, but only if you are sure you _should_ receive data from the other side. So if you sometimes have a pause in the dataflow, look for a solution using keepalives (see above).
0
 

Author Comment

by:byungho
ID: 18034197
I wrote ping/pong from server to client! But it's not work correctly.. -_-;

Now, I work ping/pong from client to server!!
0
 
LVL 1

Expert Comment

by:Computer101
ID: 21135795
Forced accept.

Computer101
EE Admin
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