Sending and receiving a TMemoryStream using IdTCPClient and IdTCPServer

delphi, indy, tcp

Solution

Just use the proper parameters:

.IOHandler.Write(ms, 0, true); //true ... indicates WriteByteCount

.IOHandler.ReadStream(ms, -1); //-1 ... use ByteCount

Problem

I found Remy Lebeau's chat demo of IdTCP components in XE2 and I wanted to play with it a little bit. (It can be found here) I would like to send a picture using these components and the best approach seems to be using TMemoryStream. If I send strings, the connection works fine, the strings are transmitted successfully, however when I change it to Stream instead, it doesn't work. Here is the code: Server ``` procedure TMainForm.IdTCPServerExecute(AContext: TIdContext); var rcvdMsg: string; ms:TMemoryStream; begin // This commented code is working, it receives and sends strings. // rcvdMsg:=AContext.Connection.IOHandler.ReadLn; // LogMessage('<ServerExec> '+rcvdMsg); // // TResponseSync.SendResponse(AContext, rcvdMsg); try ms:=TMemoryStream.Create; AContext.Connection.IOHandler.ReadStream(ms); ms.SaveToFile('c:\networked.bmp'); except LogMessage('Failed to receive',clred); end; end; ``` Client ``` procedure TfrmMain.Button1Click(Sender: TObject); var ms: TMemoryStream; bmp: TBitmap; pic: TPicture; s: string; begin // Again, this code is working for sending strings. // s:=edMsg.Text; // Client.IOHandler.WriteLn(s); ms:=TMemoryStream.Create; pic:=TPicture.Create; pic.LoadFromFile('c:\Back.png'); bmp:=TBitmap.Create; bmp.Width:=pic.Width; bmp.Height:=pic.Height; bmp.Canvas.Draw(0,0,pic.Graphic); bmp.SaveToStream(ms); ms.Position:=0; Client.IOHandler.Write(ms); ms.Free; end; ``` When I try to send the stream from the client, nothing observable happens (breakpoint in the OnExecute doesn't fire). However, when closing the programs(after sending the MemoryStream), two things happen: - If the Client is closed first, only then does the `except` part get processed (the log displays the 'Failed to receive' error. However, even if I place a breakpoint on the first line of the try-except block, it somehow gets skipped and only the error is displayed). - If the Server is closed first, the IDE doesn't change back from debug, Client doesn't change its state to disconnected (as it normally does when server disconnects) and after the Client is closed as well, an Access Violation error from the Server app appears. I guess this means that there is a thread of the Server still running and maintaining the connection. But no matter how much time i give it, it never completes the task of receiving the MemoryStream. Note: The server uses `IdSchedulerOfThreadDefault` and `IdAntiFreeze`, if that matters. As I can't find any reliable source of help for the revamped Indy 10 (it all appears to apply for the older Indy 10, or even Indy 9), I hope you can tell me what is wrong. Thanks - ANSWER - SERVER ``` procedure TMainForm.IdTCPServerExecute(AContext: TIdContext); var size: integer; ms:TMemoryStream; begin try ms:=TMemoryStream.Create; size:=AContext.Connection.IOHandler.ReadLongInt; AContext.Connection.IOHandler.ReadStream(ms, size); ms.SaveToFile('c:\networked.bmp'); except LogMessage('Failed to receive',clred); end; end; ``` CLIENT ``` procedure TfrmMain.Button1Click(Sender: TObject); var ms: TMemoryStream; bmp: TBitmap; pic: TPicture; begin ms:=TMemoryStream.Create; pic:=TPicture.Create; pic.LoadFromFile('c:\Back.png'); bmp:=TBitmap.Create; bmp.Width:=pic.Width; bmp.Height:=pic.Height; bmp.Canvas.Draw(0,0,pic.Graphic); bmp.SaveToStream(ms); ms.Position:=0; Client.IOHandler.Write(ms, 0, True); ms.Free; end; ```

Original source