[supernewbie]

вот так например

const
packet1='';
packet2='';

var
TimerCycle:integer;
timer:TTimer;

procedure Init;
begin
timer:=TTimer.Create(nil);
timer.interval:=1000;
timer.OnTimer:=@fireTimer;
timer.enabled:=true;
TimerCycle:=1; 
end;

procedure fireTimer(Sender: TObject);
begin 
case TimerCycle of
  1:begin   
  buf:=packet1;
  sendtoserver;
  Inc(TimerCycle);  
  end; 
  2:begin  
  buf:=packet2;
  sendtoserver;    
  TimerCycle:=1;  
  timer.enabled:=false;  
  end;     
end;
end;

procedure Free; 
begin
timer.free;

end;

begin

end.