libCURL timeout while receiving HTTP multi-part flow

Question

I'm using libCURL to perform an HTTP GET request toward a device that responds with a continuous flow of data in a multipart HTTP response.

I'd like to handle the unfortunate but possible case where the device is disconnected/shutdown or is not reachable anymore on the network.
By default libCURL does not have a few seconds timeout as I need, so I tried:

1. setting the CURLOPT_CONNECTTIMEOUT options,
   but this only works at connection stage, not while already receiving data.

2. setting the CURLOPT_TIMEOUT option,
   but this seems to always force a timeout even when data is still received.

My question is: how can I properly handle a timeout with libCURL, in the case described above?

Answer 1

For your scenario instead of

curl_easy_setopt(curl, CURLOPT_TIMEOUT, <your timeout in seconds>);

use

curl_easy_setopt(curl, CURLOPT_LOW_SPEED_LIMIT, 1);
curl_easy_setopt(curl, CURLOPT_LOW_SPEED_TIME, <your timeout in seconds>);

The above two lines make sure that if the average speed drops below 1 byte per second, in a time frame of X seconds, then the operation is aborted (timeout).

See reference here.