Hadoop’s namenode and datanodes expose a bunch of TCP ports used by Hadoop’s daemons to communicate to each other or listen directly to users’ requests. These ports information are needed by both the Hadoop users and cluster administrators to write programs or configure firewalls/gateways accordingly.
A post written by Philip Zeyliger from Cloudera’s blog summarizes the default ports used by Hadoop:
Hadoop Default Ports Quick Reference.
Please note that these ports are also configuration through Hadoop’s configuration, such as the DFS and jobtracker’s ports in conf/core-site.xml conf/mapred-site.xml as used in the Hadoop Installation Tutorial.
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