TmemoryStream Server Out Of Memory On receiving stream - delphi

Question

All I'm trying to do is send a stream with TSockets, but I'm having an "out of memory" error. I managed to send files, just not images. In the server Form's OnCreate event, I'm creating the stream. For the client, in the Form's OnCreate I'm creating the stream, also a bmp.
I've tried to see if it's not sending, but it's sending something, only I can't tell what. On the server side, I've tested sending commands to the client, and I know they send, also I've tested with booleans, but still get a memory error.
procedure TForm1.ServerSocket1ClientRead(Sender: TObject; Socket: TCustomWinSocket);
var
BytesReceived: Longint;
CopyBuffer: Pointer;
ChunkSize: Integer;
TempSize: Integer;
FSize: Integer;
writing: Boolean;
bmp: tbitmap;
const
MaxChunkSize: Longint = 8192;
begin
If FSize = 0 then
begin
If Socket.ReceiveLength > SizeOf(TempSize) then
begin
Socket.ReceiveBuf(TempSize, SizeOf(TempSize));
stream.SetSize(TempSize);
FSize := TempSize;
End;
End;
If (FSize > 0) and (writing) then //receiving the image
begin
GetMem(CopyBuffer, MaxChunkSize);
writing := true;
While Socket.ReceiveLength > 0 do
Begin
ChunkSize := Socket.ReceiveLength;
If ChunkSize > MaxChunkSize then
ChunkSize := MaxChunkSize;
BytesReceived := Socket.ReceiveBuf(CopyBuffer^, ChunkSize);
stream.Write(CopyBuffer^, BytesReceived);
Dec(FSize, BytesReceived);
End;
If FSize = 0 then
begin
bmp.LoadFromStream(stream);
self.Image1.Picture.Bitmap.LoadFromStream(stream);
stream.SetSize(0);
FSize := 0;
End;
FreeMem(CopyBuffer, MaxChunkSize);
writing := false;
stream.Free;
exit;
End;
end;
procedure TForm1.ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket);
var
size: Integer;
Data: string;
begin
try
CaptureImage(bmp); //i have a procedure for this & know it works
bmp.SaveToStream(stream);
size := stream.size; //sending the tbitmap image
stream.Position := 0;
Socket.SendBuf(size, sizeof(size));
Socket.SendStream(stream);
except
stream.Free;
end;

Answer 1

You are not taking FSize into account when reading data from the client. You are reading as much as the client sends, and not stopping when the stream size has been reached. And you are not taking into account that it may (and likely will) take multiple OnRead events to receive the entire image, so you may end up freeing your stream prematurely.
Also, TCustomWinSocket.SendStream() is not very stable, especially if you are using the socket in non-blocking mode. You should instead use TCustomWinSocket.SendBuf() directly in a loop and handle any socket errors as needed.
Try something more like this:
uses
..., System.Math;
procedure TForm1.ServerSocket1ClientConnect(Sender: TObject; Socket: TCustomWinSocket);
begin
Socket.Data := nil;
end;
procedure TForm1.ServerSocket1ClientDisconnect(Sender: TObject; Socket: TCustomWinSocket);
begin
if Socket.Data <> nil then
TMemoryStream(Socket.Data).Free;
end;
procedure TForm1.ServerSocket1ClientRead(Sender: TObject; Socket: TCustomWinSocket);
var
Stream: TMemoryStream;
BytesReceived: Integer;
StreamSize, TempSize: Int32;
BytesRemaining: Int64;
P: PByte;
ChunkSize: Integer;
bmp: TBitmap;
const
MaxChunkSize: Int64 = 8192;
begin
Stream := TMemoryStream(Socket.Data);
// receiving the image size
if Stream = nil then
begin
if Socket.ReceiveLength < SizeOf(TempSize) then Exit;
BytesReceived := Socket.ReceiveBuf(TempSize, SizeOf(TempSize));
if BytesReceived <= 0 then Exit;
StreamSize := ntohl(TempSize);
Stream := TMemoryStream.Create;
Socket.Data := Stream;
Stream.Size := StreamSize;
BytesRemaining := StreamSize;
end else
BytesRemaining := Stream.Size - Stream.Position;
// receiving the image
if BytesRemaining > 0 then
begin
P := PByte(Stream.Memory);
if Stream.Position > 0 then
Inc(P, Stream.Position);
repeat
ChunkSize := Integer(Math.Min(BytesRemaining, MaxChunkSize));
BytesReceived := Socket.ReceiveBuf(P^, ChunkSize);
if BytesReceived <= 0 then Exit;
Inc(P, BytesReceived);
Dec(BytesRemaining, BytesReceived);
Stream.Seek(soCurrent, BytesReceived);
until BytesRemaining = 0;
end;
// loading the image
try
bmp := TBitmap.Create;
try
Stream.Position := 0;
bmp.LoadFromStream(Stream);
Image1.Picture.Bitmap.Assign(bmp);
finally
bmp.Free;
end;
finally
Socket.Data := nil;
Stream.Free;
end;
end;
uses
..., System.Math, Winapi.WinSock;
function SendRaw(Sckt: TSocket; const Data; Size: Integer);
var
P: PByte;
BytesSent: Integer;
begin
Result := 0;
P := PByte(#Data);
while Size > 0 do
begin
BytesSent := send(Sckt, P^, Size, 0);
if BytesSent = -1 then Exit;
Inc(P, BytesSent);
Dec(Size, BytesSent);
Inc(Result, BytesSent);
end;
end;
procedure WriteToSocket(Socket: TCustomWinSocket; const Data; Size: Integer);
var
Stream: TMemoryStream;
P: PByte;
BytesSent: Integer;
begin
if Size <= 0 then Exit;
Stream := TMemoryStream(Socket.Data);
P := PByte(#Data);
if not ((Stream <> nil) and (Stream.Size > 0)) then
begin
BytesSent := SendRaw(Socket.SocketHandle, P^, Size);
if BytesSent > 0 then
begin
Dec(Size, BytesSent);
if Size = 0 then Exit;
Inc(P, BytesSent);
end;
end;
if Stream = nil then
begin
Stream := TMemoryStream.Create;
Socket.Data := Stream;
end else
Stream.Seek(soEnd, 0);
Stream.WriteBuffer(P^, Size);
end;
procedure TForm1.ClientSocket1Connect(Sender: TObject; Socket: TCustomWinSocket);
begin
Socket.Data := nil;
end;
procedure TForm1.ClientSocket1Disconnect(Sender: TObject; Socket: TCustomWinSocket);
begin
if Socket.Data <> nil then
TMemoryStream(Socket.Data).Free;
end;
procedure TForm1.ClientSocket1Write(Sender: TObject; Socket: TCustomWinSocket);
var
Stream: TMemoryStream;
BytesRemaining: Int64;
ChunkSize: Integer;
P: PByte;
begin
Stream := TMemoryStream(Socket.Data);
if Stream = nil then Exit;
BytesRemaining := Stream.Size;
if BytesRemaining = 0 then Exit;
P := PByte(Stream.Memory);
repeat
ChunkSize := Integer(Math.Min(BytesRemaining, MaxInt));
BytesSent := SendRaw(Socket.SocketHandle, P^, ChunkSize);
if BytesSent > 0 then
begin
Inc(P, BytesSent);
Dec(BytesRemaining, BytesSent);
end;
until (BytesSent < ChunkSize) or (BytesRemaining = 0);
if BytesRemaining = 0 then
Stream.Clear
else if P > Stream.Memory then
begin
MoveMemory(Stream.Memory, P, BytesRemaining);
Stream.Size := BytesRemaining;
end;
end;
procedure TForm1.ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket);
var
Stream: TMemoryStream;
bmp: TBitmap;
StreamSize, TempSize: Int32;
begin
...
Stream := TMemoryStream.Create;
try
// saving the bitmap image
bmp := TBitmap.Create;
try
CaptureImage(bmp);
bmp.SaveToStream(Stream);
finally
bmp.Free;
end;
// sending the TBitmap image
StreamSize := Stream.Size;
TempSize := htonl(StreamSize);
WriteToSocket(Socket, TempSize, sizeof(TempSize));
WriteToSocket(Socket, Stream.Memory^, StreamSize);
finally
Stream.Free;
end;
end;