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#161: How can I read the proxy information?

most tasks that works with internet, requires to read the current proxy settings from computer before connect to remote server.

Today I want to show two way to read this information.

1. to use registry
this is easy and fast way but note that if in future the Microsoft will change a key where proxy stored, you must change your code too:-)

var
  Handle: HKey;
  Buffer: array[0..256] of Char;
  BufSize: Integer;
  DataType: Integer;
begin
  if RegOpenKeyEx(HKEY_CURRENT_USER,
                  'SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings',
                  0, KEY_READ, Handle) = ERROR_SUCCESS then
  begin
    BufSize := SizeOf(Buffer);
    DataType := reg_sz;
    if RegQueryValueEx(Handle, 'ProxyServer', nil, @DataType, @Buffer, @BufSize) = ERROR_SUCCESS then
      ProxyServer := Buffer;

    BufSize := SizeOf(Integer);
    if RegQueryValueEx(Handle, 'ProxyEnable', nil, @DataType, @i, @BufSize) = ERROR_SUCCESS then
      UseProxyServer := (i <> 0);
    RegCloseKey(Handle);
  end;
end;

2. to use WinInet library
this is more correct way to get an information but require IE 3.x (or higher)

var
  ProxyInfo: PInternetProxyInfo;
  Len: LongWord;
begin
  Len := 4096;
  GetMem(ProxyInfo, Len);
  try
    if InternetQueryOption(nil, INTERNET_OPTION_PROXY, ProxyInfo, Len)
then
      if ProxyInfo^.dwAccessType = INTERNET_OPEN_TYPE_PROXY then
      begin
        UseProxyServer := True;
        ProxyServer := ProxyInfo^.lpszProxy
      end
  finally
    FreeMem(ProxyInfo);
  end;
end;

Now if proxy used, we'll receive in ProxyServer variable similar string:

"ftp=proxy.domain.com:8082;gopher=proxy.domain.com:8083;http=proxy.domai n.com:8080;https=proxy.domain.com:8081"

where domain.com is our proxy.

So as you see, now we must parse this string for correct protocol (http/ftp etc) and to get the proxy server and port number. For example:

  if UseProxyServer and (ProxyServer <> '') then
  begin
    i := Pos('http=', ProxyServer);
    if (i > 0) then
    begin
      Delete(ProxyServer, 1, i+5);
      j := Pos(';', ProxyServer);
      if (j > 0) then
        ProxyServer := Copy(ProxyServer, 1, j-1);
    end;

    i := Pos(':', ProxyServer);
    if (i > 0) then
    begin
      ProxyPort := StrToIntDef(Copy(ProxyServer, i+1, Length(ProxyServer)-i), 0);
      ProxyServer := Copy(ProxyServer, 1, i-1)
    end
  end;


Published: April 6, 2004

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