I keep receiving 0 byte from TClientSocket - delphi

Question

Using DbgView, i saw that after i receive a Stream, the server then receives 0 bytes like more than 100 times, what is this ? this is new to me, i never saw this happening.
i personally have a feeling it is a client-side issue, could it ?
this is how i receive the stream server-side:
FMemStream := Socket.ReceiveStream(FMemStreamSize, cbUpdateStreamProgBar);
try
doClientReadStreamEnd;
finally
FMemStream.Free;
FInStreamMode := False; // we're not in stream mode anymore
end;
function TCustomWinSocketHelpher.ReceiveStream(StreamLen: Integer; Callback: TUpdateProgBarProc): TMemoryStream;
const
ChunkSize = 4096; // 4kb
var
PData: PByte;
ReadAmount: Integer;
begin
Result := TMemoryStream.Create;
GetMem(PData, StreamLen);
try
while StreamLen > 0 do
begin
ReadAmount := ReceiveBuf(PData^, ChunkSize);
if (ReadAmount > 0) then
begin
Result.Write(PData^, ReadAmount);
Callback(ReadAmount); // update gui
Inc(PData^, ReadAmount); // update PData current position
Dec(StreamLen, ReadAmount); // update loop condition
end;
end;
finally
FreeMem(PData);
end;
end;
on client-side, this is how i send stream:
FClientSocket.Socket.SendStreamEx(RemoteProcedureCalls.Stream);
procedure TCustomWinSocketHelpher.SendStreamEx(Stream: TStream);
begin
Stream.Seek(0, TSeekOrigin.soBeginning);
SendStream(Stream);
end;
Here's a photo of how it looks, it should not continue sending after line 5.

Answer 1

When ReceiveBuf() returns 0, it means the socket has been disconnected by the other party. You are not handling that condition, so you keep looping, getting back 0 again and again. Any value less than 1 is a failed read and needs to be treated as such. If ReceiveBuf() returns -1, an actual read error occurred, but that result can only be returned if the error was WSAEWOULDBLOCK, which is not fatal, or you have an OnError event handler assigned that is setting ErrorCode := 0. Otherwise, ReceiveBuf() would raise an ESocketError exception on a real socket error.
Try this:
function TCustomWinSocketHelpher.ReceiveStream(StreamLen: Integer; Callback: TUpdateProgBarProc): TMemoryStream;
const
ChunkSize = 4096; // 4kb
var
PData: PByte;
ReadAmount: Integer;
begin
Result := TMemoryStream.Create;
try
GetMem(PData, ChunkSize);
try
while StreamLen > 0 do
begin
ReadAmount := ReceiveBuf(PData^, Min(ChunkSize, StreamLen));
if ReadAmount < 0 then
begin
if WSAGetLastError() = WSAEWOULDBLOCK then
Continue;
// an OnError event handler must have disabled an exception being raised
Exit;
end;
if ReadAmount = 0 then
begin
// socket disconnected
raise Exception.Create(''); // or just Exit if you don't mind that the expected data is incomplete
end;
Result.WriteBuffer(PData^, ReadAmount);
Callback(ReadAmount); // update gui
Dec(StreamLen, ReadAmount); // update loop condition
end;
finally
FreeMem(PData);
end;
except
Result.Free;
raise;
end;
end;