public void setHost(String host) {
        this.host = host;
    }
Sets the host name or IP string from where the authentication attempt occurs.  It is up to the Authenticator
implementation processing this token if an authentication attempt without a host is valid or not.
<p/>
<p>(Shiro's default Authenticator
allows <tt>null</tt> hosts to allow localhost and proxy server environments).</p>

@param host the host name or IP string from where the attempt is occurring
@since 1.0
core/src/main/java/org/apache/shiro/authc/UsernamePasswordToken.java