CODEWITHSUNDEEP
multithreadingdelphiclient-serverdelphi-7indy
user1361263
user1361263

Reputation: 101

Delphi 7 + Indy + Multithread clients

My PC is connected to two electronic devices that send data using a TCP connection. I would like to develop a Delphi program able to log all this data. In the following code I create two TCPClients using two threads. I am able to log data from one device using one thread, but when two threads are runnning the application freezes. I don´t have experience programming in Delphi, sorry if there are too many mistakes... I am using Delphi 7. What can I do to avoid freezing the app?

Thanks in advance

//************************************************************************//
type TThreadConn1 = class(TThread)
    private
    protected
        procedure Execute; override;
    end;

type TThreadConn2 = class(TThread)
    private
    protected
        procedure Execute; override;
    end;


var
    Form1: TForm1;
    TCP1: TThreadConn1;
    TCP2: TThreadConn2;
    flag1: bool;
    flag2: bool;


implementation
{$R *.dfm}

//******************************Connection 1******************************//
procedure TThreadConn1.Execute;  //Connect+loop read buffer+disconnect
begin
    Form1.IdTCPClient1.Connect;  
    While flag1 = false do   
        Form1.IdTCPClient1.CurrentReadBuffer;
    Form1.IdTCPClient1.Disconnect;
end; 

procedure TForm1.ButtonConnection1Click(Sender: TObject);
begin
    flag1:=false;
    TCP1 := TThreadConn1.Create(false);  //Launch thread 
end;

procedure TForm1.ButtonDisconnection1Click(Sender: TObject);
begin
    flag1:=true;
    if (TCP1.Terminated = false) then
        TCP1.Terminate;   //Is it ok to finish this way a thread?
    end;

//******************************Connection2******************************//
procedure TThreadConn2.Execute;  //Connect+loop read buffer+disconnect
begin
    Form1.IdTCPClient2.Connect;
    While flag2 = false do   
        Form1.IdTCPClient1.CurrentReadBuffer;
    Form1.IdTCPClient2.Disconnect;
end; { of procedure }

procedure TForm1.ButtonConnection2Click(Sender: TObject);
begin
    flag2:=false;
    TCP2 := TThreadConn2.Create(false);
end;

procedure TForm1.ButtonDisconnection2Click(Sender: TObject);
begin
    flag2:=true;
    if (TCP2.Terminated = false) then
        TCP2.Terminate;
end;
end.

Upvotes: 0

Views: 2586

Answers (2)

Remy Lebeau
Remy Lebeau

Reputation: 596332

You don't need to create two separate threads that do the same thing. Create one class and then instantiate multiple copies of it. Try this instead:

type
  TThreadConn = class(TThread)
  private
    FClient: TIdTCPClient;
  protected
    procedure Execute; override;
  public
    constructor Create(AClient: TIdTCPClient);
  end;

var
  TCP1: TThreadConn = nil;
  TCP2: TThreadConn = nil;

constructor TThreadConn.Create(AClient: TIdTCPClient);
begin
  inherited Create(False);
  FClient := AClient;
end;

procedure TThreadConn.Execute;
begin
  FClient.Connect;  
  try
    while Terminated = false do   
      FClient.CurrentReadBuffer;
  finally
    FClient.Disconnect;
  end;
end; 

procedure TForm1.ButtonConnection1Click(Sender: TObject);
begin
  TCP1 := TThreadConn.Create(TIdTCPClient1);
end;

procedure TForm1.ButtonDisconnection1Click(Sender: TObject);

begin if (TCP1 <> nil) then begin TCP1.Terminate; TCP1.WaitFor; FreeAndNil(TCP1); end; end;

procedure TForm1.ButtonConnection2Click(Sender: TObject);

begin TCP2 := TThreadConn.Create(IdTCPClient2); end;

procedure TForm1.ButtonDisconnection2Click(Sender: TObject);
begin
  if (TCP2 <> nil) then
  begin
    TCP2.Terminate;
    TCP2.WaitFor;
    FreeAndNil(TCP2);
  end;
end;

Upvotes: 1

Martin James
Martin James

Reputation: 24857

Apart from the overall design, (which you will probably fix in time, maybe with some more help), in TThreadConn2.Execute, you call Form1.IdTCPClient1.CurrentReadBuffer.

Hints:

If you want to use threads to communicate with several different clients, don't plonk TidTCPClients onto forms. This is inflexible because every time you want to add a new client, you have to plonk another instance onto the form and rebuild. It also makes for a lot of extra work to get your app to shut down cleanly which, I assure you, you will not want.

Dynamically create a TidTCPClient instance in either the TThread descendant ctor or at the top of the 'Execute' method.

Try and declare one class that can be instantiated for each client connection, so you don't have to copy/paste code, edit it and and get it wrong

Oh - for now, don't try and terminate the threads at all. In fact, forever, don't try and terminate the threads at all. In the execute, loop around connect() until successful, then read stuff in a loop, write to log, (in a thread-safe manner). Do that forever. If you wnat to stop the logging, set a 'don't log' boolean so that the thread still runs but simply doesn't bother calling the logger. Again - don't go near trying to terminate the threads.

If I get a chance over the weekend, I'll do a simple example - one form, four TEdits for two pair hostname/port and two TMemos to send data to and display data from the server.

Upvotes: 0

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