Wait for data with Indy10 - delphi

Question

I have a TCP "Server", that is sending data every 20 seconds. I am trying to receive this data and display the result. Currently, the data is displayed 3 times instead of once. It then waits another 20 seconds, and again displays the data 3 times.
with Client do
begin
Connect;
while True do
begin
try
if IOHandler.CheckForDataOnSource(1000) then
begin
WriteLn('Bytes available: ' IntToStr(IOHandler.InputBuffer.Size));
IOHandler.ReadBytes(buffer, IOHandler.InputBuffer.Size);
end;
except
on e : exception do
writeln(e.message);
end;
if(buffer <> nil) then
begin
SetString(msg, PAnsiChar(#buffer[0], length(buffer));
buffer := nil;
IOHandler.InputBuffer.Clear;
end;
write(msg);
end;
end;

Answer 1

You are calling write(msg) on every loop iteration regardless of whether you actually read any new data or not. You are resetting your buffer to nil after assigning it to msg, but you are not resetting msg to '' after writing it. So each loop iteration is writing whatever msg already holds until you assign a new value to it.
Try this code instead:
with Client do
begin
Connect;
buffer := nil;
repeat
try
if IOHandler.CheckForDataOnSource(1000) then
begin
WriteLn('Bytes available: ' + IntToStr(IOHandler.InputBuffer.Size));
IOHandler.ReadBytes(buffer, IOHandler.InputBuffer.Size);
SetString(msg, PAnsiChar(buffer), Length(buffer));
Write(msg);
buffer := nil;
end;
except
on E: Exception do
WriteLn(E.Message);
end;
until not Connected;
end;
Which can be simplified to this:
with Client do
begin
Connect;
buffer := nil;
repeat
try
IOHandler.ReadBytes(buffer, -1);
WriteLn('Bytes read: ' + Length(buffer));
SetString(msg, PAnsiChar(buffer), Length(buffer));
Write(msg);
buffer := nil;
except
on E: Exception do
WriteLn(E.Message);
end;
until not Connected;
end;
Or even:
with Client do
begin
Connect;
repeat
try
if IOHandler.CheckForDataOnSource(IdTimeoutDefault) then
begin
WriteLn('Bytes available: ' + IntToStr(IOHandler.InputBuffer.Size));
Write(IOHandler.InputBufferAsString(en8bit));
end;
except
on E: Exception do
WriteLn(E.Message);
end;
until not Connected;
end;

Answer 2

I fixed the problem I was having, by moving the write(msg) into the if statement checking if the buffer is not nil.
with Client do
begin
Connect;
while True do
begin
try
if IOHandler.CheckForDataOnSource(1000) then
begin
WriteLn('Bytes available: ' IntToStr(IOHandler.InputBuffer.Size));
IOHandler.ReadBytes(buffer, IOHandler.InputBuffer.Size);
end;
except
on e : exception do
writeln(e.message);
end;
if(buffer <> nil) then
begin
SetString(msg, PAnsiChar(#buffer[0], length(buffer));
buffer := nil;
IOHandler.InputBuffer.Clear;
write(msg); {only write out the message when the buffer is not nil}
end;
end;
end;