How to check FTP connectivity using CURL library in c?

Question

I want to check FTP server connectivity using curl library in c program. Can anyone tell me how to do that without using any data transfer means i don't want to transfer any file to check that. I want is like CURLOPT_CONNECT_ONLY option which is available for only HTTP, SMTP and POP3 protocols not for FTP.

Curl version : 7.24 Requirement : FTP server connectivity test.

Answer 1

Here in below example, Only connect request will be delivered to FTP server and if server is pingable then it will give CURLE_OK return code other wise give failure response after specific timeout(60 sec). Other options you can set as per your requirement from http://curl.haxx.se/libcurl/c/ .

...
snprintf(ftp_url, BUF_LEN_512, "ftp://%s:%s@%s", uploadConf->username, uploadConf->password, uploadConf->ip);

// Reset curl lib
curl_easy_reset(curl);

curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, throw_away);
if (CURLE_OK != (res = curl_easy_setopt(curl, CURLOPT_URL, ftp_url)))
{
    printf("Failed to check ftp url, Error : %s : %d\n", curl_easy_strerror(res), res);
}
curl_easy_setopt(curl, CURLOPT_NOBODY, 1L);

// Connection establishment timeout
curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 60);

if (CURLE_OK != (res = curl_easy_perform(curl)))
{
    /* If fail to connect */
}
else
{
    /* If connected succesfully */
}


static size_t throw_away(void *ptr, size_t size, size_t nmemb, void *data)
{
    size_t res;

    res = (size_t)(size * nmemb);

    /* we are not interested in the headers itself, so we only return the size we would have saved ... */
    return res;
}

Hope it will help you all to test connectivity to FTP server using libcurl in c.