Hi All,
What's the most reliable way of detecting whether a remote website is responding?

Thanks

Richard
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.lazarus.freepascal.org/pipermail/lazarus/attachments/20141030/1dd16e63/attachment.html>

maybe ping?

Richard Mace wrote

Hi All, What's the most reliable way of detecting whether a remote website is responding?

Get the HTTP headers:

uses
  fphttpclient;
procedure TForm1.Button1Click(Sender: TObject);
var
  VHttp: TFPHTTPClient;
  VHeaders: TStrings;
begin
  VHttp := TFPHTTPClient.Create(nil);
  VHeaders := TStringList.Create;
  try
    VHttp.RequestHeaders.Add('Connection: Close');
    VHttp.Head('http://lazarus.freepascal.org', VHeaders);
    if VHeaders.Count > 0 then
      ShowMessage('OK')
    else
      ShowMessage('Fail');
  finally
    VHeaders.Free;
    VHttp.Free;
  end;
end;

Richard,

There is no substitute for "suck it and see". I have a web server that I need to ensure keeps running. I monitor it from another system that runs a CRON job every five minutes that uses "wget" to download the home page. If this fails it EMails me.

As you are putting this on the lazarus list. I assume that you want to do something similar from an interactive Pascal program. Here there is no substitute for good error handling. My experience is with the indy components and these will raise an exception if they can't download a given webpage (timeout). You can catch this and give the user an appropriate error message when they try to access a non-responding server. You could even have a background thread to keep doing this, if it is really important to tell the user as soon as possible.

Tony Whyman
MWA

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.lazarus.freepascal.org/pipermail/lazarus/attachments/20141030/3772c5a4/attachment.html>

maybe ping?

Many servers do not respond to ping. So not reliable.

Mattias

ping might tell you if the IP address is active but that's all... it won't tell you if the server is running or servicing requests... you have to request something from the server to see if it is servicing requests... the easiest and smallest would be to request the headers (only) from the root...

+1

Like this:
http://lists.lazarus.freepascal.org/pipermail/lazarus/2014-October/089112.html

Thanks for everyone's replies, very helpful.

Richard

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.lazarus.freepascal.org/pipermail/lazarus/attachments/20141030/3fcc6f74/attachment.html>