Function connected

3rdparty/cppzmq/zmq.hpp:1921–1921

    ZMQ_DEPRECATED("from 4.7.1, use handle() != nullptr or operator bool")
    bool connected() const ZMQ_NOTHROW { return (_handle != ZMQ_NULLPTR); }

    ZMQ_CPP11_DEPRECATED("from 4.3.1, use send taking a const_buffer and send_flags")
    size_t send(const void *buf_, size_t len_, int flags_ = 0)