How to connect bitcoind mainnet node on AWS EC2 by using rpcjson? 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?
Most likely, you'll have to open that port on your EC2 instance.