[SOLVED] synapse: how to get a timeout for http-downloads to work?
lazarus / 38-Networking and Web Programming

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Hartmut · 2022-12-08 11:22

My program shall download a website with synapse. Sometimes this
website is not available. Then my code runs into a timeout of 130
seconds, which is too much. I want a timeout of max. 4 seconds.

Here is a demo of my code from a bigger program:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i {$mode
objfpc}{$H+} uses sysutils, classes, httpsend; const URL =
'http://xxx.yyy.com'; function myHttpGetText(url: string; HTTP:
THTTPSend; var SL: TStringList): boolean;   {loads URL 'url' from a
Webserver into a StringList}   var ok: boolean;   begin   ok:=false; 
 SL:=TStringList.Create;   HTTP.Clear; {Reset headers, document and
Mimetype}    if HTTP.HTTPMethod('GET',url) then       begin     
 SL.LoadFromStream(HTTP.Document);       ok:=true;       end; 
 exit(ok);   end; function download_Website(url: string; var SL:
TStringList): boolean;   var HTTP: THTTPSend;       ok: boolean; 
 begin   HTTP:=THTTPSend.Create;   HTTP.Timeout:=4000; 
 HTTP.Sock.SetTimeout(4000);   ok:=myHttpGetText(url, HTTP, SL); 
 HTTP.Free;   exit(ok);   end; var SL: TStringList;    t: TDateTime; 
 sec: double;    ok: boolean; begint:=now;ok:=download_Website(URL,
SL);sec:=(now-t)*86400.0; {time in seconds}writeln('Time: ', sec:0:2,
' seconds'); if not ok then writeln('ERROR') else
writeln(SL.Text);SL.Free;end.
I use FPC 3.2.0 on Linux Ubuntu 18.04 with synapse stable version 40
and trunk r266 (both have the same result).

What I'm doing wrong? Thanks in advance.

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balazsszekely · 2022-12-08 14:00

@Hartmut
On windows immediately returns with the message "Error". I don't have
to wait even 4 seconds.

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Hartmut · 2022-12-08 15:25

Thank you GetMem for your reply. Yes, if the URL does not exist at
all, then immediately "ERROR" is returned. But with my real URL - if
it is currently unavailable - then I have a timeout of 130 seconds,
which is too long for me.

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rvk · 2022-12-08 15:27

You probably want to set HTTP.Sock.ConnectionTimeout to whatever you
want.

See my post here:
Quote from: rvk on February 21, 2018, 09:48:45 amSorry, I spoke too
soon. What is said above still holds but the connect timeout was
discussed on the Synapse list in 2012 and the non-blockingmode (which
is mentioned above) was implemented in revision #160.

You also need to set the HTTPSender.Sock.ConnectionTimeout which
handles the Connect timeout in non-blockingmode after which the socket
is switched back to blocking mode.

Example:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i const  URL
= '10.255.255.1'; // <-- this is always non responsevar  HTTPSender:
THTTPSend;  HTTPGetResult: boolean;  Tm: TDateTime;begin  HTTPSender
:= THTTPSend.Create;  try    HTTPSender.Timeout := 1 * 1000;   
HTTPSender.Sock.ConnectionTimeout := 1 * 1000;    Tm := Now;   
HTTPGetResult := HTTPSender.HTTPMethod('GET', URL);    Tm := Now -
Tm;    ShowMessage(Format('%d: done in %.3f seconds',
[HTTPSender.ResultCode, Tm * 24 * 60 * 60]));  finally   
HTTPSender.Free;  end;end;
PS. When ConnectionTimeOut > 0 then Synapse will connect in non-
blocking mode.
In blocking mode (the default) there is no way to set the timeout.
See http://www.ararat.cz/synapse/doku.php/public:howto:connecttimeout

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Hartmut · 2022-12-08 16:51

Great! 'HTTPSender.Sock.ConnectionTimeout' works perfectly. Thanks a
lot rvk.
Again I like synapse and it's capabilities.