Failed to discover master?

Hi

i'm using elastic search server install in Debian server.for creating
index i used Rabbitmq river.when i start to read the message.
my program can not discover my master[elastic server].i had made
change on /etc/elasticsearch.yml where i mention the

network:

       host:192.168.21.201

but my program it unable to get the elastic cluster.please help me to
resolve this problem.

Thanks