Markus Koetter's man page updates for the FTPPORT ranges

just a '-' symbol to let the library use your system's default IP

address. Default FTP operations are passive, and thus won't use PORT.

Starting in 7.19.5, you can append \&":[start]-[end]\&" to the right of the

address, to tell libcurl what TCP port range to use. That means you specify a

port range, from a lower to a higher number. A single number works as well,

but do note that it increases the risk of failure since the port may not be

available.

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 will pick a free port.  If a range is provided and all ports in the

range are not available, libcurl will report CURLE_FTP_PORT_FAILED for the

handle.  Invalid port/range settings are ignored.  IPv6 addresses followed by

a port or portrange have to be in brackets.  IPv6 addresses without port/range

specifier can be in brackets.  (added in 7.19.5)

Examples with specified ports:

.nf

  eth0:0

  192.168.1.2:32000-33000

  curl.se:32123

  [::1]:1234-4567

.fi

You disable PORT again and go back to using the passive version by setting

this option to NULL.