Argument list too long libcurl c program error

Question

I am using a C program to connect to an ftp server and upload a file. Previously the server was not using SSL and I was able to do the file upload using the following code :

curl_global_init(CURL_GLOBAL_ALL);

curl = curl_easy_init();

if(curl)
{

    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, throw_away);

    curl_easy_setopt(curl, CURLOPT_USERNAME, "username");
    curl_easy_setopt(curl, CURLOPT_PASSWORD, "password");

    if (CURLE_OK != (res = curl_easy_setopt(curl, CURLOPT_URL, "ftp://ftpb.****.com")))
    {
        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, 20);
    printf("Trying to connect...\n");
    if (CURLE_OK != (res = curl_easy_perform(curl)))
    {
        /* If fail to connect */
        printf("FTP connection failed...%s : %d\n", strerror(res), res);
    }
    else
    {
        /* If connected succesfully */
        printf("Connected to FTP successfully...\n");

      /****** proceed with upload ******/
    }
}

After the ftp server switched to use SSL certification, I added the following line to my code to use SSL:

    curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);

Now, when I run the program, my application fails to connect to FTP and show the message :

"FTP connection failed...Argument list too long : 7"

The same error is obtained even if I do not add the CURLOPT_USE_SSL part.

I am able to connect to the ftp server using Filezilla (only if I add ftps to the address). Adding ftps in my code gives the error:

"FTP connection failed...Device not a stream : 60"

Anybody knows a workaround for this?

Answer 1

You cannot use strerror() on a return code from libcurl. libcurl provides its own strerror() version for its return codes. See curl_easy_strerror .

You can also see the errors on the libcurl-errors man page, and there you learn that 7 means CURLE_COULDNT_CONNECT: "Failed to connect() to host or proxy" . This is probably because you don't run the ftp server on port 21 which is the default port for FTP.

The error 60 you then mention is CURLE_SSL_CACERT which indicates you got further but libcurl failed to verify your server.

Answer 2

I was able to fix the issue by adding the line

curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);

The application does not try to validate the SSL certificates now and proceeds with the connection