org.apache.http.conn.HttpHostConnectException: Connection to http://xx.xx.xx.xxx refused

we have developed mobile app which communicates with Amazon web server (AWS) it is running on micro instance. the APIs are being hosted on AWS server. mobile app is pushing data to server on every 5 seconds. Our app is running on more than 50 devices and very device pushing the data to server on every 5 seconds due to this, mobile app is getting an exception "org.apache.http.conn.HttpHostConnectException: Connection to http://xx.xx.xx.xxx refused". can you please assist me how we can resolve this error.

Note, we are not using RDC on AWS. we have installed Mysql database in EC2 instance.

Thanks for your help.