Are you running from in the local instance or connected any VPN.
Please confirm that you gave your IP and the system name in the host entry.
make sure the instance is up.
I went to tools > Embedded OC4J Server Preferences
under Global > Startup
I am using my local host IP address, which is not over a VPN connection. I'll then go to my EAM_HM_MAIN.xml page under my application sources folder for my project, right-click > run.
I am not sure what piece I am missing.
Under Tools > Embedded OC4J Server Preferences > Global > Startup, can you try setting 'Host Name or IP Address...' to 'Default Local IP Address'.
HTTP 500 internal server error mostly related to the data base connection.
so 1st check if you have correct dbc file in your JDeveloper folder.
the dbc file contain the database connection and server details,so its very important to have correct dbc file attached in the project properties.
also check the login credentials for oracle application in project properties.