Nodes communicate with each other through the p2p protocol which is open. The API port is only used by the wallet and the proxy mode, and SSL is optional but usually recommended.
All of this has no relation to the security of the blockchain itself.
hi what is meant by "proxy mode"?
the p2p protocol is only open to other nodes I am assuming that no "bunk" code can be injected in there through an open peer port with no SSL?
Sorry for asking these types of questions I am not a programmer really but would love to understand as much as possible.
"proxy mode" or what we call light client is a mode of operation for the wallet that doesn't require the download of the blockchain. It picks, at random, open API nodes from the network and all queries are done through those nodes. The private key is never sent to those node, as always the transactions are signed locally.