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Re: Maximum number of parallel connections?

From: Daniel Stenberg <>
Date: Fri, 18 Feb 2011 22:12:14 +0100 (CET)

On Fri, 18 Feb 2011, Felix E. Klee wrote:

> Sorry if this is off topic, may be an OS issue.
> I wrote a daemon for downloading data from web-services using cURL
> Multi. The daemon runs on a 32bit Amazon EC2 instance with the Amazon
> Linux AMI (CentOS).
> Now, I wonder: How many downloads can be run in parallel? What are the
> limiting factors?

libcurl itself has no actual limits apart from memory restraints.

If you use the "plain" multi interface, it will get a problem with more than
1024 sockets if libcurl was built to use select() instead of poll(), and as
the API is very select()-centered it very well might cause a problem there

If you use that many connections (really, even you even just use them in the
hundreds) you really should use the multi_socket anyway to reach proper

If you use the multi_socket API, libcurl has no limitation at all.

If you do multiple connections to the same server(s), many servers of course
reject too many connections coming from the same client and in general reject
connections once it reaches its limit.

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Received on 2011-02-18