Reading unknown amount of bytes from IdTCPServer connection in delphi - delphi

Question

I am setting up a client/server program to send and receive unknown amount of byte in my application. How to receive unknown buffer size in my program?
I pass my data to TIdBytes variable and sending it with this line:
IdTCPClient.IOHandler.Write(TIdBytes_Var);
The first byte of TIdBytes_Var determine packet size and varies due to other condition. I take care of the size of the package to not exceed 1024 byte.
On the receiver side (IdTCPServerExecute) I add this line to read all bytes:
var
byte_buffer: TIdBytes;
begin
AContext.Connection.IOHandler.ReadBytes(byte_buffer,-1,false);
end;
On debugging mode, after I send first packet from client to the server, an exception is raised:
raised exception class EConvertError with message ''' is not a valid floating point value
And on running mode only loss my connection.
Where is the problem, and how can I receive all bytes from Indy's input buffer?
Here is my minimal code:
In the client making packet and finally set event that is passed to other thread
//create packet. Buffer_to_send is a TIdBytes variable on unit of network thread (U_network_thread).
SetLength(U_network_thread.Buffer_to_send,(6 + (tmp_ints * 12)));//set buffer lenght dynamically, tmp_ints is my record counter(shortint)
tmp_int:= 2;//tmp_int is the integer variable
U_network_thread.Buffer_to_send[0]:= $1;//header sign
U_network_thread.Buffer_to_send[1]:= tmp_ints;//tmp_ints is my record counter as short integer
while tmp_ints > 0 do
begin
Read(My_File,tmp_rec);//read record from bin file
Move(tmp_rec,U_network_thread.Buffer_to_send[tmp_int],12);//12 is record lenght
tmp_int:= tmp_int + 12; //add pointer
dec(tmp_ints);
end;
tmp_int2:= zone_i;//integer info
Move(tmp_int2,U_network_thread.Buffer_to_send[tmp_int],4); //add info to the packet
Frq_Evt.SetEvent; //set event to triger sending on other thread
On the net_thread, after connecting to the server and receive ack sign by ReadLn command, I wait for event
procedure TNetThread.Execute;
.//create IdTCPClient1 and connect to server
.//receive ack from server by IdTCPClient1.IOHandler.ReadLn command
.//wait for event
while(true) do
if (FEvent.WaitFor(200) = wrSignaled) then//Buffer_to_send fill on main thread
begin
//send buff
if sending_buf(Buffer_to_send) then
begin
//sending ok
end
else
begin
//sending error
end;
end;
end;
end;
function TNetThread.sending_buf(T_Buffer: TIdBytes): boolean;
begin
try
IdTCPClient1.IOHandler.Write(T_Buffer)
result := true;
except
result := false;
end;
end;
On the server side, after connecting, sending ack sign by WriteLn command, and on the IdTCPServerExecute I try to do
procedure Tmain_form.IdTCPServerExecute(AContext: TIdContext);
var
byte_buffer: TIdBytes;
begin
AContext.Connection.IOHandler.ReadBytes(byte_buffer,-1,false);
//do something else
end;
All work fine and connection passed and server send ack sign to client. Client receive it and wait for event. After event occurs, client making up packet and pass it to net_thread. Packet is good and sending is too. But on the server side raise the problem.

Answer 1

the first byte of TIdBytes_Var determine packet size and varies due to other condition.
So, then simply read 1 byte first, then read how many additional bytes it says, eg :
AContext.Connection.IOHandler.ReadBytes(byte_buffer, AContext.Connection.IOHandler.ReadByte, false);
I take care of the size of the package to not exceed 1024 byte.
A single byte can not exceed 255, so your max packet size would be 256, including the size byte.
on debugging mode after i send first packet from client to the server rise a problem and receive:
"raised exception class EConvertError with message ''' is not a valid floating point value"
There is no way the code you have shown can raise that exception.
Update
Here is my minimal code
Seeing your code now, I can see that despite your earlier claim, the first byte of your packet is NOT a packet size, it is always $01. In fact, there is no packet size stored in the packet at all. The 2nd byte contains the number of 12-byte records stored in the packet, and the packet has 6 fixed bytes, so the max packet size is actually 3066 bytes.
Try something more like this:
passed to other thread
// create packet. Buffer_to_send is a TIdBytes variable on unit of network thread (U_network_thread).
SetLength(U_network_thread.Buffer_to_send, (6 + (tmp_ints * 12))); // set buffer length dynamically, tmp_ints is my record counter(shortint)
tmp_int := 2; // tmp_int is the integer variable
U_network_thread.Buffer_to_send[0] := $1; //header sign
U_network_thread.Buffer_to_send[1] := tmp_ints; // tmp_ints is my record counter as short integer
while tmp_ints > 0 do begin
Read(My_File, tmp_rec); // read record from bin file
Move(tmp_rec, U_network_thread.Buffer_to_send[tmp_int], 12); // 12 is record length
Inc(tmp_int, 12); // add pointer
Dec(tmp_ints);
end;
tmp_int2 := GStack.HostToNetwork(UInt32(zone_i)); // integer info, in network byte order
Move(tmp_int2, U_network_thread.Buffer_to_send[tmp_int], 4); // add info to the packet
Frq_Evt.SetEvent; // set event to trigger sending on other thread
procedure Tmain_form.IdTCPServerExecute(AContext: TIdContext);
var
byte_buffer: TIdBytes;
Header: Byte;
Count: Word;
Zone: Integer;
begin
Header := AContext.Connection.IOHandler.ReadByte; // should always be $01
Count := AContext.Connection.IOHandler.ReadByte; // record counter
AContext.Connection.IOHandler.ReadBytes(byte_buffer, Count * 12); // records
Zone := AContext.Connection.IOHandler.ReadInt32; // zone
// process as needed...
end;