In order to connect agent and server, you need to add each agent to the server.
   Run the 'manage_agents' to add or remove them:

   /var/ossec/bin/manage_agents

Starting OSSEC HIDS v2.6 (by Trend Micro Inc.)...
OSSEC analysisd: Testing rules failed. Configuration error. Exiting.
Started ossec-maild...
Started ossec-execd...
Started ossec-analysisd...
Started ossec-logcollector...
Started ossec-remoted...
Started ossec-syscheckd...

<global>
    <email_notification>yes</email_notification>
    <email_to>*****@gmail.com</email_to>
    <smtp_server>localhost</smtp_server>
    <email_from>ossecm@localhost.localdomain</email_from>
  </global>

Started ossec-monitord...
Completed.

<smtp_server>localhost</smtp_server>
 <email_to>example@example.com</email_to>