How to use the portend.free function in portend

def start(self, port, *args, **config):
        config.update(self.config)
        config['server.socket_port'] = port
        portend.free('localhost', port)
        server = self[port] = subprocess.Popen((sys.executable, '-m', self.module, '-c', json.dumps(config)) + args)
        portend.occupied('localhost', port)
        server.started = time.time()
        assert not server.poll()
        return clients.Resource('http://localhost:{}'.format(port))

def check_port_availability(host, port):
    """
    Make sure the port is available for the server to start.
    """
    try:
        portend.free(host, port, timeout=PORT_AVAILABILITY_CHECK_TIMEOUT)
    except portend.Timeout:
        # Bypass check when socket activation is used
        # https://manpages.debian.org/testing/libsystemd-dev/sd_listen_fds.3.en.html#ENVIRONMENT
        if not os.environ.get("LISTEN_PID", None):
            # Port is occupied
            logger.error(
                "Port {} is occupied.\n"
                "Please check that you do not have other processes "
                "running on this port and try again.\n".format(port)
            )
            sys.exit(1)

def start(self):
        """Start the HTTP server."""
        if self.running:
            self.bus.log('Already serving on %s' % self.description)
            return

        self.interrupt = None
        if not self.httpserver:
            raise ValueError('No HTTP server has been created.')

        if not os.environ.get('LISTEN_PID', None):
            # Start the httpserver in a new thread.
            if isinstance(self.bind_addr, tuple):
                portend.free(*self.bind_addr, timeout=Timeouts.free)

        import threading
        t = threading.Thread(target=self._start_http_thread)
        t.setName('HTTPServer ' + t.getName())
        t.start()

        self.wait()
        self.running = True
        self.bus.log('Serving on %s' % self.description)
    start.priority = 75

def start(self):
        """Start the HTTP server."""
        if self.running:
            self.bus.log('Already serving on %s' % self.description)
            return

        self.interrupt = None
        if not self.httpserver:
            raise ValueError('No HTTP server has been created.')

        if not os.environ.get('LISTEN_PID', None):
            # Start the httpserver in a new thread.
            if isinstance(self.bind_addr, tuple):
                portend.free(*self.bind_addr, timeout=Timeouts.free)

        import threading
        t = threading.Thread(target=self._start_http_thread)
        t.setName('HTTPServer ' + t.getName())
        t.start()

        self.wait()
        self.running = True
        self.bus.log('Serving on %s' % self.description)
    start.priority = 75

def find_free_port(host, currentport):
    """ Return a free port, 0 when nothing is free """
    n = 0
    while n < 10 and currentport <= 49151:
        try:
            portend.free(host, currentport, timeout=0.025)
            return currentport
        except:
            currentport += 5
            n += 1
    return 0

abort_and_show_error(browserhost, cherryport)
        except:
            abort_and_show_error(browserhost, cherryport, '49')

    # Windows instance is reachable through registry
    url = None
    if sabnzbd.WIN32 and not new_instance:
        url = get_connection_info()
        if url and check_for_sabnzbd(url, upload_nzbs, autobrowser):
            exit_sab(0)

    # SSL
    if enable_https:
        port = https_port or cherryport
        try:
            portend.free(browserhost, port, timeout=0.05)
        except IOError as error:
            if str(error) == 'Port not bound.':
                pass
            else:
                if not url:
                    url = 'https://%s:%s%s/api?' % (browserhost, port, sabnzbd.cfg.url_base())
                if new_instance or not check_for_sabnzbd(url, upload_nzbs, autobrowser):
                    # Bail out if we have fixed our ports after first start-up
                    if sabnzbd.cfg.fixed_ports():
                        abort_and_show_error(browserhost, cherryport)
                    # Find free port to bind
                    newport = find_free_port(browserhost, port)
                    if newport > 0:
                        # Save the new port
                        if https_port:
                            https_port = newport

# Determine web host address
    cherryhost, cherryport, browserhost, https_port = get_webhost(cherryhost, cherryport, https_port)
    enable_https = sabnzbd.cfg.enable_https()

    # When this is a daemon, just check and bail out if port in use
    if sabnzbd.DAEMON:
        if enable_https and https_port:
            try:
                portend.free(cherryhost, https_port, timeout=0.05)
            except IOError:
                abort_and_show_error(browserhost, cherryport)
            except:
                abort_and_show_error(browserhost, cherryport, '49')
        try:
            portend.free(cherryhost, cherryport, timeout=0.05)
        except IOError:
            abort_and_show_error(browserhost, cherryport)
        except:
            abort_and_show_error(browserhost, cherryport, '49')

    # Windows instance is reachable through registry
    url = None
    if sabnzbd.WIN32 and not new_instance:
        url = get_connection_info()
        if url and check_for_sabnzbd(url, upload_nzbs, autobrowser):
            exit_sab(0)

    # SSL
    if enable_https:
        port = https_port or cherryport
        try:

# Set root folders for HTTPS server file paths
    sabnzbd.cfg.set_root_folders2()

    if ipv6_hosting is not None:
        sabnzbd.cfg.ipv6_hosting.set(ipv6_hosting)

    # Determine web host address
    cherryhost, cherryport, browserhost, https_port = get_webhost(cherryhost, cherryport, https_port)
    enable_https = sabnzbd.cfg.enable_https()

    # When this is a daemon, just check and bail out if port in use
    if sabnzbd.DAEMON:
        if enable_https and https_port:
            try:
                portend.free(cherryhost, https_port, timeout=0.05)
            except IOError:
                abort_and_show_error(browserhost, cherryport)
            except:
                abort_and_show_error(browserhost, cherryport, '49')
        try:
            portend.free(cherryhost, cherryport, timeout=0.05)
        except IOError:
            abort_and_show_error(browserhost, cherryport)
        except:
            abort_and_show_error(browserhost, cherryport, '49')

    # Windows instance is reachable through registry
    url = None
    if sabnzbd.WIN32 and not new_instance:
        url = get_connection_info()
        if url and check_for_sabnzbd(url, upload_nzbs, autobrowser):