UDP File Transfer Using Delphi Indy 10

Question

I am using Delphi Xe-3 indy 10 for udp file transfer . I am passing file in small chunks and I am facing problem while transfering bigger and files other than text files.

In client when I debug the size of the file is saved wrong ,I am unable to figure out the reason. Below is the client and server code, Client send files to Server. (I am using udp because I am working on Reliable udp.)

Problem is mentioned in the client code(send function).

Server:

procedure TForm2.serverUDPRead(AThread: TIdUDPListenerThread;
  AData: array of Byte; ABinding: TIdSocketHandle);
  var

  str , len :string;
  size : word;
  index : word;

begin

   setlength(b,length(Adata));
   move(Adata[0],b[0],length(Adata));              // convert array of byte to tidbytes

   index:=0;
   setlength(Ext,b[index]);                      // get filename length
   setlength(File_data , b[index+1]);             // get file length
   index:= index+2;
   move(b[index],Ext[1],length(Ext)*2);           // copy filename
   index:= index+length(Ext)*2;
   move(b[index],File_data[0],length(File_data));      // copy file

   save.Visible:= true;
   //progressbar1.Visible:= true;
   progressbar1.Position
   memo1.Lines.Add('Receving file...->');

end;

procedure TForm2.SaveClick(Sender: TObject);
var
buttonSelected : Integer;
content:integer;
begin

savedialog1.FileName := Ext;            // save file name
if savedialog1.Execute then            // save dialog opens
   try
    if FileExists(SaveDialog1.FileName) then
     begin
     if MessageDlg('Do you want to overwrite the existing file ?',
     TMsgDlgType.mtConfirmation,mbYesNo,0) = IDNO then
       begin
         exit;
       end
     end;

    Strm:=TFileStream.Create(Ext,fmCreate);
    Strm.Position:=0;
    //progressbar1.Value:= 100*length(File_data)/content;                                                // set position to start
    WriteTIdBytesToStream (Strm,File_data,length(File_data),0);      // write bytes data to stream
    memo1.Lines.Add('File transmission complete...');
    finally
    strm.Free;
    save.Visible := false;
    progressbar1.Visible := false;
    end;

end;

Client:

procedure TForm1.LoadClick(Sender: TObject);
begin

//openDialog1.InitialDir := GetCurrentDir;

if openDialog1.Execute then

begin
Edit1.Text     := OpenDialog1.FileName;
memo1.Lines.Add (Opendialog1.FileName);

Filename := ExtractFileName (Opendialog1.FileName);
Mem := TFileStream.Create(OpenDialog1.FileName,fmOpenRead); //connects the client

end;

{finally
opendialog1.Free;
end;
    }

end;

procedure TForm1.SendClick(Sender: TObject);
var
size : word;
index : word;
begin
index := 0;
 try
   Posi:=0;
   While Posi<Mem.Size do
   begin
   Len:=1024;
   if Mem.Size-Posi<1024 then
   begin
   Len:=Mem.Size-Posi;
   end;
   setlength(chunk,len);
   ReadTIdBytesFromStream(Mem,chunk,Len);

  size := length(chunk) + length(Filename)*2 + 2;  // it gets right sizes here , 
                                                   //chunk size is also correct
  setlength(File_data,Size);
  File_data[index] := length(Filename);
  index:= index+1;
  File_data[index]:= length(chunk);// its saved here ,value is reduced.
  index:= index+1;
  move(Filename[1],File_data[index],length(Filename)*2);
  index:= index+length(Filename)*2;
  move(chunk[0],file_data[index],length(chunk));

  client.SendBuffer('127.0.0.1',6002,File_data);
  Inc(Posi,Len);
  end;

  finally
  Mem.Free;
  Edit1.Text:='';
  Filename:='';
  end;

end;

procedure TForm1.FormCreate(Sender: TObject);
begin
client.Bindings.Add.Port:= 0;
client.Active  := true;
end;

end.

Answer 1

Indy has TIdTrivialFTP and TIdTrivialFTPServer components. TFTP is a UDP-based file transfer protocol. You should consider using that instead of creating your own custom protocol.