skipis set to 1, it instructs libcurl to not use the IP address the server suggests in its 227-response to libcurl's PASV command when libcurl connects the data connection. Instead libcurl will re-use the same IP address it already uses for the control connection. But it will use the port number from the 227-response.
This option thus allows libcurl to work around broken server installations that due to NATs, firewalls or incompetence report the wrong IP address back.
This option has no effect if PORT, EPRT or EPSV is used instead of PASV.