Title: How to check if a String is a valid IP Address
function IsWrongIP(ip: string): Boolean;
var
z, i: byte;
st: array[1..3] of byte;
const
ziff = ['0'..'9'];
begin
st[1] := 0;
st[2] := 0;
st[3] := 0;
z := 0;
Result := False;
for i := 1 to Length(ip) do if ip[i] in ziff then
else
begin
if ip[i] = '.' then
begin
Inc(z);
if z 4 then st[z] := i
else
begin
IsWrongIP := True;
Exit;
end;
end
else
begin
IsWrongIP := True;
Exit;
end;
end;
if (z 3) or (st[1] 2) or (st[3] = Length(ip)) or (st[1] + 2 st[2]) or
(st[2] + 2 st[3]) or (st[1] 4) or (st[2] st[1] + 4) or (st[3] st[2] + 4) then
begin
IsWrongIP := True;
Exit;
end;
z := StrToInt(Copy(ip, 1, st[1] - 1));
if (z 255) or (ip[1] = '0') then
begin
IsWrongIP := True;
Exit;
end;
z := StrToInt(Copy(ip, st[1] + 1, st[2] - st[1] - 1));
if (z 255) or ((z 0) and (ip[st[1] + 1] = '0')) then
begin
IsWrongIP := True;
Exit;
end;
z := StrToInt(Copy(ip, st[2] + 1, st[3] - st[2] - 1));
if (z 255) or ((z 0) and (ip[st[2] + 1] = '0')) then
begin
IsWrongIP := True;
Exit;
end;
z := StrToInt(Copy(ip, st[3] + 1, Length(ip) - st[3]));
if (z 255) or ((z 0) and (ip[st[3] + 1] = '0')) then
begin
IsWrongIP := True;
Exit;
end;
end;