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llibcurl (version 7.87.0) - FTP Keep Connection Alive Issue

From: Nagesh, Rahul \[AUTOSOL/MSOL/IN\] via curl-library <>
Date: Tue, 10 Jan 2023 12:18:09 +0000

Hello All,

I have recently updated libcurl.dll to version in my application for secure FTP operations and earlier we were using libcurl.dll version
After upgrading libcurl.dll to latest version we are facing issue to keeping FTP connection active when no FTP operation performed for more than 1.5 minutes.
To keep the FTP connection alive with PureFTP server our application is sending following set of FTP commands to server after every 3 minutes,

curl_slist_append(pstCurlCmdList, CURL_PWD_COMMAND)
curl_slist_append(pstCurlCmdList, "NOOP")
curl_slist_append(pstCurlCmdList, "REST 0")
curl_slist_append(pstCurlCmdList, "STAT")
curl_slist_append(pstCurlCmdList, "NOOP")

After establishing FTP connection successfully with PureFTP server, we are not performing any FTP operation for 3 minutes and after every 3 minutes we are sending above commands.
with latest libcurl.dll version our FTP client application receiving curl error response to these commands i.e., CURLE_OPERATION_TIMEDOUT (28).
And we are unable to use existing libcurl FTP connection handle throughout.

Also, we have set initial CURLOPT_CONNECTTIMEOUT_MS to more than 3 minutes. Still, we are getting CURLE_OPERATION_TIMEDOUT (28) error response from FTP server.

However, when same set of commands were sent using libcurl.dll version that time FTP client application receiving CURLE_OK (0) response from PureFTP server
in above scenario and we were able to use existing libcurl FTP connection handle.

We want to use the latest 'libcurl.dll' version i.e., 7.87.0 in my application.
So, it will be helpful if you provide some details to fix above FTP keep connection alive issue while using libcurl version

Also please let me know if you need any other additional details.

Note: There is no change in FTP server side.


Rahul Nagesh | Direct +91 020 4200 1840 | WWW:<>

Received on 2023-01-10