Returns an object containing various state info.

"version": xxxxx, (numeric) the server version
"protocolversion": xxxxx, (numeric) the protocol version
"walletversion": xxxxx, (numeric) the wallet version
"balance": xxxxxxx, (numeric) the total bitcoin balance of the wallet
"blocks": xxxxxx, (numeric) the current number of blocks processed in the server
"timeoffset": xxxxx, (numeric) the time offset
"connections": xxxxx, (numeric) the number of connections
"proxy": "host:port", (string, optional) the proxy used by the server
"difficulty": xxxxxx, (numeric) the current difficulty
"testnet": true|false, (boolean) if the server is using testnet or not
"keypoololdest": xxxxxx, (numeric) the timestamp (seconds since GMT epoch) of the oldest pre-generated key in the key pool
"keypoolsize": xxxx, (numeric) how many new keys are pre-generated
"unlocked_until": ttt, (numeric) the timestamp in seconds since epoch (midnight Jan 1 1970 GMT) that the wallet is unlocked for transfers, or 0 if the wallet is locked
"paytxfee": x.xxxx, (numeric) the transaction fee set in btc/kb
"relayfee": x.xxxx, (numeric) minimum relay fee for non-free transactions in btc/kb
"errors": "..." (string) any error messages

> bitcoin-cli getinfo
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getinfo", "params": [] }' -H 'content-type: text/plain;'
Don't trust. Verify. Docs extracted from src/rpcmisc.cpp#L43-L71.