<aura:event type="COMPONENT">
        <aura:attribute name="message" type="String" default="111"/>
    </aura:event>

<aura:component>
        <aura:attribute name="msg" type="String"/>
        <aura:registerEvent name="cmpEvent" type="c:ceEvent"/>
        <aura:handler name="cmpEvent" event="c:ceEvent" action="{!c.handleComponentEvent}"/>
        <lightning:button label="Get msg" onclick="{!c.getMsg}" />
        <p>{!v.msg}</p>
    </aura:component>

({
        handleComponentEvent : function(cmp, event) {
            var cmpEvent = cmp.getEvent("cmpEvent");
            var message = cmpEvent.getParam("message");
            cmp.set("v.msg", message);
            alert(message);
        },

        getMsg : function(cmp, event) {
            var cmpEvent = cmp.getEvent("cmpEvent");
            var message = cmpEvent.getParam("message");
            alert(message);
        },
    })

<aura:component>
        <aura:attribute name="messageFromEvent" type="String"/>
        <aura:handler name="cmpEvent" event="c:ceEvent" action="{!c.handleComponentEvent}"/>
        <aura:registerEvent name="cmpEvent" type="c:ceEvent"/>
        <lightning:button label="Send msg" onclick="{!c.fireComponentEvent}" />
        <c:ceNotifier />
    </aura:component>

({
        handleComponentEvent : function(cmp, event) {
            var message = event.getParam("message");
            cmp.set("v.messageFromEvent", message);
            alert(message);
        },

        fireComponentEvent : function(cmp, event) {
            var cmpEvent = cmp.getEvent("cmpEvent");
            cmpEvent.setParams({"message" : "Here we go"});
            cmpEvent.fire();
            alert(cmpEvent.getParam("message"));
        }
    })

<aura:application >
        <c:ceHandler/>
    </aura:application>