CURLOPT_FTPPORT(3) Library Functions Manual CURLOPT_FTPPORT(3)

CURLOPT_FTPPORT - make FTP transfer active

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_FTPPORT, char *spec);

Pass a pointer to a null-terminated string as parameter. It specifies that the FTP transfer should be made actively and the given string is used to get the IP address to use for the FTP PORT instruction.

The PORT instruction tells the remote server to do a TCP connect to our specified IP address. The string may be a plain IP address, a hostname, a network interface name (under Unix) or just a '-' symbol to let the library use your system's default IP address. Default FTP operations are passive, and does not use the PORT command.

The address can be followed by a ':' to specify a port, optionally followed by a '-' to specify a port range. If the port specified is 0, the operating system picks a free port. If a range is provided and all ports in the range are not available, libcurl reports CURLE_FTP_PORT_FAILED for the handle. Invalid port/range settings are ignored. IPv6 addresses followed by a port or port range have to be in brackets. IPv6 addresses without port/range specifier can be in brackets.

Examples with specified ports:


We strongly advise against specifying the address with a name, as it causes libcurl to do a blocking name resolve call to retrieve the IP address. That name resolve operation does not use DNS-over-HTTPS even if CURLOPT_DOH_URL(3) is set.

Using anything else than "-" for this option should typically only be done if you have special knowledge and confirmation that it works.

You disable PORT again and go back to using the passive version by setting this option to NULL.

The application does not have to keep the string around after setting this option.



int main(void)
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL,
    curl_easy_setopt(curl, CURLOPT_FTPPORT, "-");
    res = curl_easy_perform(curl);

Port range support was added in 7.19.5

Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.


2024-05-22 libcurl