[R] RCurl slow when sending data over 1kb

[Abiel X Reinhart]

I am using RCurl's curlPerform command to send an XML string to an HTTP server running on the localhost. The command is something like this:

reader <- basicTextGatherer()
curlPerform(url="http://127.0.0.1/", 
	httpheader=c('Content-Type' = "text/xml; charset=utf-8"), 
	postfields=toString.XMLNode(xmlRoot(xdoc)),
	writefunction=reader$update,
	.opts=curlOptions(noproxy="*"))

When sending a short string, the web server responds instantly. However, when the content-length gets above 1024 bytes, the server takes about 2 seconds to receive all the content that is being sent to it. I've written the server myself in Python, so I can see that the delay occurs while the server is fetching the data from the client, and not at any other point in the response process. Note that the delay is constant above 1024 bytes; i.e. the delay doesn't double when the content length goes up to 2048.

Using another client (Excel's MSXML2.ServerXMLHTTP library) yields no delays regardless of the content length. There are no significant differences as far as I can tell in the headers that are being sent.

Is curl somehow throttling my connection? I suppose it could be a server-side issue, but the fact that other clients don't generate the same problems makes me think it is curl.

Thanks.
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