def get_host_port(hostport_str):
    """
    Convert string in format `host:port` to host and port.
    """
    host_port_args = hostport_str.split(':') #assume argument 1 on form host:port
    rotctld_host = host_port_args[0]
    rotctld_port = 4533
    if len(host_port_args) > 1:
        rotctld_port = int(host_port_args[1])
    return rotctld_host, rotctld_port