ServerSocket only receive one time - delphi

Question

I'm trying send a record over clientsocket and receive on serversocket, everything works well but only on first time, after send one time i need disconnect clientsocket, connect again to send it again.
If somebody can help me.
here is the server side code how i receive the informations:
procedure TForm1.ServerSocket1ClientRead(Sender: TObject; Socket: TCustomWinSocket);
var
LBuffer: TBytes;
LMessageBuffer: TBytes;
LDataSize: Integer;
LProtocol: TProtocol;
begin
LDataSize := Socket.ReceiveLength;
if LDataSize >= szProtocol then begin
try
Socket.ReceiveBuf(LBuffer, SizeOf(LBuffer));
LProtocol := BytesToProtocol(LBuffer);
// check client command and act accordingly
case LProtocol.Command of
cmdConnect: begin
Memo1.Lines.Add(Format('[%s][%s][%s]', ['Connect', LProtocol.Sender.UserName, TimeToStr(LProtocol.Sender.ID)]));
end; // cmdConnect: begin
cmdDisconnect: begin
Memo1.Lines.Add(Format('[%s][%s][%s]', ['Disconnect', LProtocol.Sender.UserName, TimeToStr(LProtocol.Sender.ID)]));
end; // cmdDisconnect: begin
end;
finally
ClearBuffer(LBuffer);
end;
end;
end;
and here the client side:
var
LBuffer: TBytes;
LProtocol: TProtocol;
x : Integer;
begin
InitProtocol(LProtocol);
LProtocol.Command := cmdConnect;
ClientData.UserName := Edit1.Text;
ClientData.ID := Now;
LProtocol.Sender := ClientData;
LBuffer := ProtocolToBytes(LProtocol);
try
ClientSocket1.Socket.SendBuf(LBuffer, Length(LBuffer));
finally
ClearBuffer(LBuffer);
end;
record declaration:
type
TCommand = (
cmdConnect,
cmdDisconnect,
cmdMessageBroadcast,
cmdMessagePrivate,
cmdScreenShotGet,
cmdScreenShotData);
// client information structure, you can extend this based on your needs
type
TClient = record
UserName: string[50];
ID: TDateTime;
end; // TClient = record
// size of the client information structure
const
szClient = SizeOf(TClient);
Thanks :)

Answer 1

TBytes is a dynamic array, but you are treating it as if it were a static array.
In your client code, you are not sending LBuffer correctly. Being a dynamic array, LBuffer is just a pointer to data that is stored elsewhere in memory. So, you need to dereference LBuffer to pass the correct memory address to SendBuf().
In your server code, you are not even allocating any memory for LBuffer at all before reading bytes into it. And, like in the client, you need to dereference LBuffer when passing it to ReceiveBuf(). You also need to use the correct byte size when telling ReceiveBuf() how many bytes to read (SizeOf(TBytes) is the wrong value to use).
Lastly, you need to pay attention to the return values of SendBuf() and ReceiveBuf(), as they CAN return that fewer bytes than requested were processed! So, you should be calling SendBuf() and ReceiveBuf() in a loop.
Try this:
var
LBuffer: TBytes;
LProtocol: TProtocol;
LBufferPtr: PByte;
LBufferLen: Integer;
LNumSent: Integer;
begin
InitProtocol(LProtocol);
LProtocol.Command := cmdConnect;
ClientData.UserName := Edit1.Text;
ClientData.ID := Now;
LProtocol.Sender := ClientData;
LBuffer := ProtocolToBytes(LProtocol);
LBufferPtr := PByte(LBuffer);
LBufferLen := Length(LBuffer);
repeat
LNumSent := ClientSocket1.Socket.SendBuf(LBufferPtr^, LBufferLen);
if LNumSent = -1 then
begin
// if ClientSocket1.ClientType is set to ctNonBlocking,
// uncomment this check ...
{
if WSAGetLastError() = WSAEWOULDBLOCK then
begin
// optionally call the Winsock select() function to wait
// until the socket can accept more data before calling
// SendBuf() again...
Continue;
end;
}
// ERROR!
ClientSocket1.Close;
Break;
end;
Inc(LBufferPtr, LNumSent);
Dec(LBufferLen, LNumSent);
until LBufferLen = 0;
end;
procedure TForm1.ServerSocket1ClientRead(Sender: TObject; Socket: TCustomWinSocket);
var
LBuffer: TBytes;
LDataSize: Integer;
LProtocol: TProtocol;
LBufferPtr: PByte;
LBufferLen: Integer;
LNumRecvd: Integer;
begin
LDataSize := Socket.ReceiveLength;
if LDataSize < szProtocol then Exit;
SetLength(LBuffer, szProtocol);
repeat
// since you are validating ReceiveLength beforehand, ReceiveBuf()
// *should not* return fewer bytes than requested, but it doesn't
// hurt to be careful...
LBufferPtr := PByte(LBuffer);
LBufferLen := szProtocol;
repeat
LNumRecvd := Socket.ReceiveBuf(LBufferPtr^, LBufferLen);
if LNumRecvd <= 0 then Exit;
Inc(LBufferPtr, LNumRecvd);
Dec(LBufferLen, LNumRecvd);
Dec(LDataSize, LNumRecvd);
until LBufferLen = 0;
LProtocol := BytesToProtocol(LBuffer);
// check client command and act accordingly
case LProtocol.Command of
cmdConnect: begin
Memo1.Lines.Add(Format('[%s][%s][%s]', ['Connect', LProtocol.Sender.UserName, TimeToStr(LProtocol.Sender.ID)]));
end;
cmdDisconnect: begin
Memo1.Lines.Add(Format('[%s][%s][%s]', ['Disconnect', LProtocol.Sender.UserName, TimeToStr(LProtocol.Sender.ID)]));
end;
end;
until LDataSize < szProtocol;
end;
That being said, TClientSocket and TServerSocket have been deprecated for a LONG time. They are not even installed by default anymore (but are still available if you need to install them). You should really consider switching to another socket library that handles these kind of details for you, such as Indy's TIdTCPClient and TIdTCPServer (Indy is preinstalled in Delphi), eg:
type
PTIdBytes = ^TIdBytes;
var
LBuffer: TBytes;
LProtocol: TProtocol;
begin
InitProtocol(LProtocol);
LProtocol.Command := cmdConnect;
ClientData.UserName := Edit1.Text;
ClientData.ID := Now;
LProtocol.Sender := ClientData;
LBuffer := ProtocolToBytes(LProtocol);
// TBytes and TIdBytes are technically the same thing under the hood,
// but they are still distinct types and not assignment-compatible,
// so using a dirty hack to pass a TBytes as a TIdBytes without having
// to make a copy of the bytes...
IdTCPClient1.IOHandler.Write(PTIdBytes(#LBuffer)^);
end;
procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
type
PTBytes = ^TBytes;
var
LBuffer: TIdBytes;
LProtocol: TProtocol;
// note: TIdTCPServer is a multi-threaded component, so you must
// sync with the main thread when accessing the UI...
procedure AddToMemo(const AStr: string);
begin
TThread.Synchronize(nil,
procedure
begin
Memo1.Lines.Add(AStr);
end
);
end;
begin
// ReadBytes() can allocate the buffer for you...
AContext.Connection.IOHandler.ReadBytes(LBuffer, szProtocol);
// using a similar dirty hack to pass a TIdBytes as a TBytes
// without making a copy of the bytes ...
LProtocol := BytesToProtocol(PTBytes(#LBuffer)^);
// check client command and act accordingly
case LProtocol.Command of
cmdConnect: begin
AddToMemo(Format('[%s][%s][%s]', ['Connect', LProtocol.Sender.UserName, TimeToStr(LProtocol.Sender.ID)]));
end;
cmdDisconnect: begin
AddToMemo(Format('[%s][%s][%s]', ['Disconnect', LProtocol.Sender.UserName, TimeToStr(LProtocol.Sender.ID)]));
end;
end;
end;