boost::urls::ipv6_address::is_unspecified Return true if the address is unspecified Synopsis Declared in header <boost/url/ipv6_address.hpp> bool is_unspecified() const noexcept; Description The address 0:0:0:0:0:0:0:0 is called the unspecified address. It indicates the absence of an address. 2.5.2. The Unspecified Address (rfc4291)