为什么hdfs namenode和datanode都在一个随机端口上监听0.0.0.0.0.0 ?

I installed a new hadoop-2.2.0 today, I found after hdfs is started (using /sbin/start-dfs.sh), namenode and datanode both always listen on 0.0.0.0 at a random port? I cannot find relate configuration on I installed a new hadoop-2.2.0 today, I found a