判断IP地址是否非法！

判断IP地址是否非法的代码：
 1 function   TForm1.IsIPString(IPStr:   string):   Boolean;
 2   var
 3       i,DotNum:integer;
 4       Tmpstr:string;
 5   begin
 6       Result:=true;
 7       DotNum:=0;
 8       for   i:=1   to   Length(IPStr)   do
 9           Case   IPStr[i]   of
10               '0'..'9','.':
11                   begin
12                   if   IPStr[i]<>'.'   then
13                       begin
14                           Tmpstr:=Tmpstr+IPStr[i];
15                           if   StrtoInt(tmpstr)>255     then
16                           begin
17                               Result:=False;
18                               exit;
19                           end;
20                       end
21                   else
22                       begin
23                           if   (TmpStr='')and(DotNum>0)   then     //如果连续2个点的情况
24                           begin
25                               Result:=False;
26                               Exit;
27                           end;
28                           Tmpstr:='';
29                           DotNum:=DotNum+1;
30                       end;
31                   end;
32               else
33                   begin   Result:=false;   exit;   end;
34           end;
35       if   DotNum<>3   then   Result:=False;
36   end;