public void clear() {
        this.completedSends.clear();
        this.completedReceives.clear();
        this.completedSendBuffers.clear();
        this.disconnected.clear();
        this.connected.clear();
    }
Simulate a server disconnect. This id will be present in {@link #disconnected()} on
the next {@link #poll(long)}.
clients/src/test/java/org/apache/kafka/test/MockSelector.java