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I am experimenting with writing a program that does not rely on LineMode
to send and receive data. The following procedure is attached to a
server component:
TriggerWriteDebug is my own event, which at this time only outputs text
to a TMemo.
Also, I plan on changing the code to except Network Byte Order numeric
data, but for now I want to get this out of the way. :-)
procedure TMySockServer.ClientDataAvailable(Sender: TObject; ErrCode: Word);
var
I: Integer;
Buff: Array[0.._MAX_BUFF - 1] of Byte;
begin
TriggerWriteDebug('DataAvailable() enter...');
if (TMySockServerClient(Sender).State <> wsClosed) then
begin
I := ReadFully(Sender, @Buff, 5);
end;
TriggerWriteDebug('DataAvailable() exit.');
end;
ReadFully is another procedure I have written in hopes that I can then
read an entire string, word, integer, what have you and read until I
gather up enough data to continue (since I'm not using LineMode).
function TMySockServer.ReadFully(Sender: TObject; Data: Pointer;
BytesExpected: Integer): Integer;
var
Buffer: PChar;
Offset: Integer;
Received: Integer;
begin
Offset := 1;
GetMem(Buffer, BytesExpected);
while (BytesExpected > 0) do
begin
Received := TMySockServerClient(Sender).Receive(@Buffer[Offset],
BytesExpected);
if (Received > 0) then
begin
Offset := Offset + Received;
BytesExpected := BytesExpected - Received;
end;
end;
TriggerWriteDebug(Buffer);
Result := Offset;
end;
I have a couple of questions:
When I output Buffer in the last lines of ReadFully(), if I have a
client that sends "blah!" (which is five characters), the Memo has a
non-displayable character (but shows up on the Memo as a black block)
and then 'blah!'. So I'm not sure if I'm grabbing the string correctly.
I hope with minimal changes that this procedure might also grab numbers
without error, too.
When my test client disconnects from the server, the server enters its
ClientDataAvailable event and does not exit, which is why I have a "if
(TMySockServerClient(Sender).State <> wsClosed)" line in my
ClientDataAvailable - I was hoping that I could detect whether or not
the socket is still connected and only then try to read data. As of
right now, it stays in DataAvailable and my server goes into an infinite
loop. :(
I realize the advantages of a LineMode = TRUE. I may just switch, but
at the current time I'm just trying to learn more about sockets and
building custom protocols in general.
Does anyone have any advice for me to make these routines operational or
more robust?
Cheers,
Wes
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