Udp image streaming, delphi indy10

Question

i'm using delphi xe4 with indy10 component and i want to send an image from an Tidudpclient to Tidudpserver. I already done this operation with tcp component,but the same code didn't work with udp. how i can do this? Thanks in advance!

Timage(client)--->streamUDP-->Timage(server)

CLIENT SIDE----------------------------------------------- SEND IMAGE

var
    pic: tbitmap;
       Strm : TMemoryStream;
        img2:Timage;

    buffer:TIdBytes;
    begin

        try
          img2:=Timage.Create(nil);
          pic:=Tbitmap.Create;
          Takekpic(pic);     
          BMPtoJPG(pic,img2);
          Strm := TMemoryStream.Create;
          img2.Picture.bitmap.SaveToStream(strm);
          Strm.Position:=0;
          ReadTIdBytesFromStream(Strm,buffer,SizeOf(Strm),0);
          IdTrivialFTPServer1.SendBuffer('192.168.17.128',1234,buffer);
        finally
             strm.Free;
          end; 
    end;

SERVER SIDE---------------------------------------------------- READ IMAGE

procedure TForm6.IdTrivialFTP1UDPRead(AThread: TIdUDPListenerThread;
  const AData: TIdBytes; ABinding: TIdSocketHandle);
    var
Strm : TMemoryStream;
Jpg: TJpegImage;

begin
      Strm := TMemoryStream.Create;
      try    

         WriteTIdBytesToStream(Strm,AData,SizeOf(AData),0);
         strm.Position:=0;
         Jpg := TJpegImage.Create;
         jpg.LoadFromStream(Strm);  <---- error while reading (JPEG Error #53)
         img1.Picture.assign(jpg);
      finally
         strm.Free;
         Jpg.Free;
      end;
end;

what can be wrong in this code?

Answer 1

TIdUDPClient and TIdUDPServer do not support sending/receiving TStream data. You can save your image data into a TStream, but you will have to send/receive it using TIdBytes chunks.

Alternatively, use TIdTrivialFTP and TIdTrivialFTPServer instead, which implement TFTP, a UDP-based file transfer protocol. They operate using TStream objects

Update: for example:

Client:

var
  bmp: TBitmap;
  jpg: TJPEGImage;
  Strm : TMemoryStream;
begin
  Strm := TMemoryStream.Create;
  try
    jpg := TJPEGImage.Create;
    try
      bmp := TBitmap.Create;
      try 
        Takekpic(bmp);     
        jpg.Assign(bmp);
      finally
        bmp.Free;
      end;
      jpg.SaveToStream(Strm);
    finally
      jpg.Free;
    end;
    Strm.Position := 0;
    {
    These can be assigned ahead of time...
    IdTrivialFTP1.Host := '192.168.17.128';
    IdTrivialFTP1.Port := 1234;
    }
    IdTrivialFTP1.Put(Strm, 'image.jpg');
  finally
    Strm.Free;
  end; 
end;

Server:

procedure TForm6.IdTrivialFTPServer1WriteFile(Sender: TObject; var FileName: String; const PeerInfo: TPeerInfo; var GrantAccess: Boolean; var AStream: TStream; var FreeStreamOnComplete: Boolean) of object;
begin
  if FileName = 'image.jpg' then
  begin
    GrantAccess := True;
    AStream := TMemoryStream.Create;
    FreeStreamOnComplete := True;
  end else
    GrantAccess := False;
end;

{
If you set TIdTrivialFTPServer.ThreadedEvent to False, this event handler
runs in the context of the main thread, so the UI can be accessed safely.
If you set IdTrivialFTPServer.ThreadedEvent to True, this event handler
runs in the context of a worker thread, so you will have to manually
synchronize with the main thread when updating the UI...
}
procedure TForm6.IdTrivialFTPServer1TransferComplete(Sender: TObject; const Success: Boolean; const PeerInfo: TPeerInfo; var AStream: TStream; const WriteOperation: Boolean);
var
  jpg: TJPEGImage;
begin
  if WriteOperation and Success then
  begin
    jpg := TJPEGImage.Create;
    try
      AStream.Position := 0;
      jpg.LoadFromStream(AStream);
      img1.Picture.Assign(jpg);
    finally
      jpg.Free;
    end;
  end;
end;