send and recive TStringStream with indyTcp server and client - delphi

Question

I am trying to send a TStringStream from client to server, then send it back from server to client, using Indy TCP components.
Here is my client code:
var
Jpg: TJPEGImage;
StringStream: TStringStream;
strcams, StringImageData: String;
byt, i: integer;
procedure SendCommandWithParams(Command, Params: String);
begin
Lock;
try
if not FTCP.Connected then
begin
exit;
end;
FTCP.Socket.WriteLn('1' + Command, IndyTextEncoding_UTF8);
FTCP.Socket.WriteLn(Params, IndyTextEncoding_UTF8);
finally
Unlock;
end;
end;
begin
Jpg := TJPEGImage.Create;
StringStream := TStringStream.Create('');
try
try
Jpg.Performance := jpBestSpeed;
Jpg.ProgressiveEncoding := True;
Jpg.ProgressiveDisplay := True;
Jpg.Assign(Image2.Picture.Bitmap);
Jpg.CompressionQuality := 25;
Jpg.Compress;
Jpg.SaveToStream(StringStream);
StringImageData := StringStream.DataString;
strcams := '<[S:' + IntToStr(Length(StringImageData)) + 'B]>' +
StringImageData;
if Length(strcams) < byt then
begin
SendCommandWithParams('SIMGSEND', strcams + sep + 'IMGID5423' + sep);
end;
except
on e: exception do
//
end;
finally
StringImageData := '';
FreeAndNil(Jpg);
FreeAndNil(StringStream);
end;
end;
I can receive the TStringStream data, but the data received is corrupted, and some times it gets replaced with the second parameter that I send which is 'IMGID5423' + sep. I am not sure if this is because of some limit of packet sending through TCP so the data does not arrive complete, or is this a parser issue?
My current parser should separate each text that ended with #13#10. Here is how it looks:
var
ReceiveParams, ReceiveStream: Boolean;
S: string;
Command: String;
begin
Command := Fholdcommand;
ReceiveParams := false;
ReceiveStream := false;
if Command[1] = '1' then // command with params
begin
Command := Copy(Command, 2, MaxInt);
ReceiveParams := True;
end;
if ReceiveParams then // params incomming
begin
S := FTCP.Socket.ReadLn(IndyTextEncoding_UTF8);
FCMD := Command;
FPRMS := S;
FSTREAM := false;
if Assigned(FOnCallbackProc) then
begin
Synchronize(DoCallbackProc);
end;
end;
I am still confused about the real issue. I try to send the TStringStream in a local procedure, and it is received normally without any corruption.
Am I sending the data wrong altogether through Indy?
This is how I am receiving the data:
procedure CreateJpg(Data:string);
var
StringStream : TStringStream;
JpegImage : TJPEGImage;
Bitmap : TBitmap;
tmpPos:integer;
pp:string;
label check;
begin
GData := Data;
if LeftStr(GData,4) = '<[S:' then
begin
tmpPos := Pos(WideString('B]>'),GData);
pp := Copy(GData,5,tmpPos-5);
CDataELen := StrToInt(pp); //MidStr(st,5,tmppos - 5);
CData := RightStr(GData,length(GData)-(tmppos+2));
goto check;
end;
CData := CData + GData;
check:
//if CDataELen = length(CData) then
begin
StringStream := TStringStream.Create('');
JpegImage := TJpegImage.Create;
StringStream.WriteString(CData);
CData := '';
try
try
StringStream.Seek(0, soFromBeginning);
JpegImage.LoadFromStream(StringStream);
Bitmap := TBitmap.Create;
with Bitmap do
begin
Canvas.Lock;
try
Width := JpegImage.Width;
Height := JpegImage.Height;
Canvas.Draw(0, 0, JpegImage);
finally
Canvas.Unlock;
end;
end;
img.Picture.Bitmap.Width := Bitmap.Width;
img.Picture.Bitmap.Height := Bitmap.Height;
img.Picture.Bitmap.Canvas.Draw(0, 0, Bitmap);
except
on E: Exception do
//
end;
finally
FreeAndNil(StringStream);
FreeAndNil(JpegImage);
FreeAndNil(Bitmap);
end;
end;
end;

Answer 1

The problem is that you are saving the JPG binary data to a TStringStream and then letting it reinterpret the binary data as if it were string data. You can't do that. You need to save the JPG data to a binary stream instead, like TMemoryStream, and then encode the binary data using a string-safe encoding, like Base64.
Try something more like this instead:
uses
..., IdCoder, IdCoderMIME;
...
var
Jpg: TJPEGImage;
JpegStream: TMemoryStream;
strcams, StringImageData: String;
begin
try
JpegStream := TMemoryStream.Create;
try
Jpg := TJPEGImage.Create;
try
Jpg.Performance := jpBestSpeed;
Jpg.ProgressiveEncoding := True;
Jpg.ProgressiveDisplay := True;
Jpg.Assign(Image2.Picture.Bitmap);
Jpg.CompressionQuality := 25;
Jpg.Compress;
Jpg.SaveToStream(JpegStream);
finally
Jpg.Free;
end;
JpegStream.Position := 0;
StringImageData := TIdEncoderMIME.EncodeStream(JpegStream);
finally
JpegStream.Free;
end;
strcams := '<[S:' + IntToStr(Length(StringImageData)) + 'B]>' + StringImageData;
SendCommandWithParams('SIMGSEND', strcams + sep + 'IMGID5423' + sep);
except
on e: exception do
//
end;
end;
And then on the receiving end:
procedure CreateJpg(Data: string);
var
JpegStream: TMemoryStream;
JpegImage: TJPEGImage;
Bitmap: TBitmap;
tmpPos, tmpLen: integer;
pp: string;
begin
try
if not TextStartsWith(Data, '<[S:') then
begin
// bad data, do something else...
Exit;
end;
tmpPos := Pos('B]>', Data);
pp := Copy(Data, 5, tmpPos-5);
tmpLen := StrToInt(pp);
Data := Copy(Data, tmpPos+3, tmpLen);
Bitmap := TBitmap.Create;
try
JpegImage := TJpegImage.Create;
try
JpegStream := TMemoryStream.Create;
try
TIdDecoderMIME.DecodeStream(Data, JpegStream);
JpegStream.Position := 0;
JpegImage.LoadFromStream(JpegStream);
finally
JpegStream.Free;
end;
with Bitmap do
begin
Canvas.Lock;
try
Width := JpegImage.Width;
Height := JpegImage.Height;
Canvas.Draw(0, 0, JpegImage);
finally
Canvas.Unlock;
end;
end;
finally
JpegImage.Free;
end;
img.Picture.Assign(Bitmap);
finally
Bitmap.Free;
end;
except
on E: Exception do
//
end;
end;

Answer 2

Your problem appears to be that you are treating binary data as though it is text. Binary data can contain anything, for instance #13#10 line breaks or indeed anything whatsoever.
If you wish to send that data as text, then you need to use a text encoding. For example, encode it as base64.
Or transmit the content as binary rather than text.