I'd like to access bitocind mainnet node on AWS EC2 from ruby. I've written as follows using rpcjson, however it cannot connect, then returned the error

client = RPC::JSON::Client.new 'http://rpcuser:rpcpassword@publicIP:8332', 1.1

Operation timed out - connect(2) for publicIP port 8332

publicIP is the Public IP shown on EC2 instance page.

On the other hand, when I wrote as follows in order to connect localhost testnet node, it has no problem.

client = RPC::JSON::Client.new 'http://rpcuser:rpcpassword@127.0.0.1:8332', 1.1

Could you tell me what is the problem?