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Re: ECHO responses

From: Hans H. Anderson <>
Date: Tue, 6 May 2003 10:29:10 -0500 (CDT)


The problem for the retries with is that if
gets the request and processes it, but we don't get a response, the next
retry is a "duplicate". I do retry, but almost always hit this wall.

The problem could be in many places, but since I noticed that doesn't seem to allow pings or traceroutes, I thought maybe
something in the Curl system was using ECHO packets to test for server
whereabouts in some cases. If not, then I'll look elsewhere.

Thanks for the response,


On Tue, 6 May 2003, Ralph Mitchell wrote:

> Curl doesn't need to use ECHO. It set a couple of timers (--connect-timeout
> and --max-time) then requests the webpage and waits for a response. If the
> server doesn't respond at all, you'll get the connect timeout. If the server
> allows the connection but is slow to provide the web page, you'd eventually
> hit the max time timeout.
> The difference between curl and a browser is that curl doesn't automatically
> retry the request. That's up to you to write into your scripts...
> I guess to emulate a browser more closely, both --connect-timeout and
> --max-time ought to be kept small and the request issued multiple times in
> the event of timeouts.
> Ralph Mitchell
> "Hans H. Anderson" wrote:
> > I'm using Curl to interact with (using OpenSSL). This
> > usually works great, but it times out sometimes, even while there is no
> > obvious long-term outage or problem with my or's server. I
> > have the timeout set high, up to 40 seconds.
> >
> > I tried traceroute and ping to the servers and it apparently
> > rejects them (is silent). There is no response, but at the same time, I
> > can use their servers for normal transactions. I'm guessing they were
> > getting a lot of ping attacks and such so they just stopped responding to
> > ECHO requests.
> >
> > The reason I bring all this up is that I'm guessing that Curl uses some
> > sort of ECHO packet when determining the timeout: request sent to server,
> > no immediate response, ping to find server, no response, timeout? Am I in
> > the ballpark? I'm not a C programmer or I'd be able to figure it out
> > myself.
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Received on 2003-05-06