Using Anonymous Proxy Servers

Problem/Question/Abstract:

If I am blocked from accessing a website because my ip address is banned, how do I bypass this?

Answer:

If you are writing Internet applications, there may come across a time when your application is blocked from accessing a website. You will get error 403 – “your IP address is on a blocked list”. In my case it happened that we had been given permission to use the data (owned by D) except it was in a website (owned by W).  W didn’t like us pulling D’s data even though D had given us permission. The data was extracted every night by a Delphi web application.

For many people this will rarely be a problem because their IP address is allocated dynamically by their ISP. But if yours is static, you need to use an Anonymous Proxy Server. These are ip addresses which you plug into Internet Explorer or HTTP components (such as the ones provided by Winshoes). Anonymous Proxy Servers can be simple Perl scripts that people setup. They can last hours, days or months but do not rely on them. One day they are there- next day- gone. What is important is that the ip address that is logged by the server is the ip of the anonymous proxy, not yours.

You can set the proxy server manually. The code below lets you get the Proxy Server in Ie under Windows Nt 4.0 so that it can be plugged into the HTTPGET component. It has not been tested under Windows 95, 98 or 2000.  ieproxyip is the dotted quad part of the ip address and ieproxyport is the port (usually but not always 80).

References to 10.0.0.2 are the local proxy server. Change these to your own.

procedure GetIEProxy(var ieproxyip: string; var ieproxyport: Integer);
var
  Registry: TRegistry;
  S: string;
  Index: Integer;
  keylist: TStringList;
  KeyName: string;

  procedure GetProxyDetails;
  var
    S, AproxyStr: string;
    Lastfound: Boolean;

    function SkipTo(Marker: string; var Text: string): string;
    var
      P: Integer;
    begin
      Marker := UpperCase(Marker);
      Lastfound := False;
      P := Pos(Marker, UpperCase(Text));
      if P > 0 then
      begin
        result := Copy(Text, P, Length(Text));
        Lastfound := True;
      end
      else
        result := '';
    end;

    function skipforward(N: Integer; ftext: string): string;
    begin
      Result := Copy(ftext, N + 1, 1000);
    end;

    function Skippast(const Marker: string; var Text: string): string;
    var
      tlf: Boolean;
    begin
      Result := SkipTo(Marker, Text);
      tlf := Lastfound;
      if Lastfound then
        Result := skipforward(Length(Marker), Result);
      Lastfound := tlf;
    end;

    function Textupto(const Marker: string; var Text: string): string;
    var
      P: Integer;
    begin
      Result := '';
      Lastfound := False;
      P := Pos(UpperCase(Marker), UpperCase(Text));
      if P > 0 then
      begin
        Result := Copy(Text, 1, P - 1);
        Text := Copy(Text, P, Length(Text));
        Lastfound := True;
      end;
    end;

  begin
    S := Registry.ReadString('ProxyServer');

    if Pos('://', S) > 0 then
    begin
      repeat
        S := Skippast('://', S);
        if Pos(';', S) > 0 then
          AproxyStr := Textupto(';', S)
        else
          AproxyStr := S;
      until not Lastfound or (Pos('10.0.0.2', AproxyStr) = 0);
    end
    else
      AproxyStr := S;

    ieproxyip := '';
    ieproxyport := 80; // Default
    if Index > 0 then
    begin
      Index := Pos(':', AproxyStr); // find port
      if Index = 0 then
        ieproxyip := AproxyStr
      else
      begin
        ieproxyip := trim(Copy(AproxyStr, 1, Index - 1));
        try
          ieproxyport := StrToInt(trim(Copy(AproxyStr, Index + 1, 10)));
        except
        end;
      end;
    end;
  end;

begin
  Registry := TRegistry.Create;
  Registry.Access := Key_read;
  keylist := TStringList.Create;
  Registry.RootKey := HKEY_CURRENT_USER;
  if Registry.OpenKeyReadOnly('Software\Microsoft\Protected Storage System Provider')
    then
  begin
    Registry.GetKeyNames(keylist);
    S := keylist[0];
  end
  else
    Exit;
  KeyName := S;
  Registry.RootKey := HKEY_USERS;

  if Registry.OpenKey(KeyName, False) then
    if Registry.HasSubkeys then
    begin
      KeyName := 'Software\Microsoft\Windows\CurrentVersion\Internet Settings';
      if Registry.OpenKey(KeyName, False) then
      begin
        GetProxyDetails;
      end;
    end;
  Registry.Free;
end;

A good source of proxy server addresses is www.deny.de