I'm using libcurl-7.19.7 to post JSON to an HTTP server. I'm aware this is an old version. I'm using the multi interface, and I based my implementation on the example given in asiohiper.cpp. I worked around bug #62.
Problem: I observe incomplete transmission of request bodies larger than about 40K bytes. Smaller requests are successful.
I set Content-{Type,Length} myself. I have tried the following two ways of supplying the body to libcurl:  1) CURLOPT_POSTFIELDS with CURLOPT_POSTFIELDSIZE, and  2) CURLOPT_READFUNCTION with CURLOPT_READDATA.
In case #1, tcpdump shows that libcurl only sends partial data. The remote server acks each packet sent.
In case #2, my logs show that libcurl only invokes my read callback for some of the data, usually no more than two 16 KiB buffers worth.
In both cases, the transfer eventually times out because the remote server does not respond to the incomplete post.
Any pointers? Thanks in advance.
Regards,Sean

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Received on 2016-08-04