hadoop-a small doubt

Hi,
   I am SreeDeepya doing MTech in IIIT.I am working on a project named cost effective and scalable storage server.I configured a small hadoop cluster with only two nodes one namenode and one datanode.I am new to hadoop.
I have a small doubt.

Can a system not in the hadoop cluster access the namenode or the datanode????If yes,then can you please tell me the necessary configurations that has to be done.

Thanks in advance.

SreeDeepya