@Override
  public void run() {
    SimpleRpcServer.LOG.debug(getName() + ": starting");
    try {
      doRunLoop();
    } finally {
      SimpleRpcServer.LOG.info(getName() + ": stopping");
      try {
        writeSelector.close();
      } catch (IOException ioe) {
        SimpleRpcServer.LOG.error(getName() + ": couldn't close write selector", ioe);
      }
    }
  }
Sends responses of RPC back to clients.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/SimpleRpcServerResponder.java