Bugs item #2783090, was opened at 2009-04-28 20:51
Message generated for change (Comment added) made by bagder
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Category: http
>Group: bad behaviour
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Constantine Sapuntzakis (csapuntz)
Assigned to: Daniel Stenberg (bagder)
Summary: Uploads slow on Windows - nonblocking send issue

Initial Comment:
Upload speeds are capped at 80kb/sec due to a Windows Sockets API behavior w/non-blocking sockets and send.

The issue and an incorrect fix are described in Microsoft KB article: http://support.microsoft.com/kb/823764

Setting the setsockopt handler below fixed the problem:

static int set_sockopts(void * clientp, curl_socket_t sockfd, curlsocktype purpose) {
    // See http://support.microsoft.com/kb/823764
#ifdef _WIN32
    int val = CURL_MAX_WRITE_SIZE * 2 + 32;
    setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, (const char *)&val, sizeof(val));
#endif

    return 0;
}

I suggest this setsockopt logic be integrated into libcurl to save others from spending a day or more tracking down the issue.

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>Comment By: Daniel Stenberg (bagder)
Date: 2009-04-28 22:27

Message:
Thanks for the report and details. I've now committed a fix, but I made the
buffer only 32 bytes larger as friends at MS confirmed that to be enough.

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Received on 2009-04-28