geth访问公有链

同步以太坊，配置rpc地址

mkdir /opt/blockchain
nohup geth --syncmode "fast" --cache=1024 --maxpeers 30 --datadir /opt/blockchain --rpc --rpcapi db,eth,net,web3,personal,admin,miner --rpcport 8545 --rpcaddr 0.0.0.0 --rpccorsdomain "*" &

https://www.51chain.net/portal/book/EthereumFrontierGuide/JSONRPCAPI-121.html
https://luren5.gitbooks.io/dapp-develop/content/43-调用json-rpc-api.html

curl -X POST -H "Content-Type: application/json" --data '{"jsonrpc": "2.0", "method": "web3_clientVersion", "params": [], "id": 1}'  http://127.0.0.1:8545
 
# 返回 {"jsonrpc":"2.0","id":1,"result":"Geth/v1.7.3-stable-4bb3c89d/linux-amd64/go1.9.2"}

JSON-RPC methods

web3_clientVersion
web3_sha3

net_version
net_peerCount
net_listening

eth_protocolVersion
eth_syncing
eth_coinbase
eth_mining
eth_hashrate
eth_gasPrice
eth_accounts
eth_blockNumber
eth_getBalance
eth_getStorageAt
eth_getTransactionCount
eth_getBlockTransactionCountByHash
eth_getBlockTransactionCountByNumber
eth_getUncleCountByBlockHash
eth_getUncleCountByBlockNumber
eth_getCode
eth_sign
eth_sendTransaction
eth_sendRawTransaction
eth_call
eth_estimateGas
eth_getBlockByHash
eth_getBlockByNumber
eth_getTransactionByHash
eth_getTransactionByBlockHashAndIndex
eth_getTransactionByBlockNumberAndIndex
eth_getTransactionReceipt
eth_getUncleByBlockHashAndIndex
eth_getUncleByBlockNumberAndIndex
eth_getCompilers
eth_compileLLL
eth_compileSolidity
eth_compileSerpent
eth_newFilter
eth_newBlockFilter
eth_newPendingTransactionFilter
eth_uninstallFilter
eth_getFilterChanges
eth_getFilterLogs
eth_getLogs
eth_getWork
eth_submitWork
eth_submitHashrate

db_putString
db_getString
db_putHex
db_getHex

shh_post
shh_version
shh_newIdentity
shh_hasIdentity
shh_newGroup
shh_addToGroup
shh_newFilter
shh_uninstallFilter
shh_getFilterChanges
shh_getMessages

# too many file open
prlimit -n150000 -p $(pidof geth)

# 关于 fast full light三种同步模式
Depending on your internet connection, and how fast your computer is, it can take a few hours, a few days, possibly even a few weeks. Yes, you can stop and resume at any time. It is a peer to peer technology that is designed to work with unstable networks, and with peers that go online and offline regularly. After you turn it back on it will pick up where it left off and start synchronizing again.

Geth has the `—fast` option which can be used the first time you start downloading the blockchain. This reduces the amount of data that has to be downloaded by cutting out the parts that don’t absolutely need to be there when you get the chain for the first time. This option only works if you are syncing the blockchain from the beginning though. If you stop it part way through you cannot resume in fast mode. After fast mode is complete, it automatically switches you to full mode going forward.

Geth also has the new experimental `—light` mode. Rather than downloading the complete chain, it downloads only the headers, then relies on the network for any other data it needs.

Using fast mode, the blockchain size will be about 30GB or less, but then will switch to full mode, and continue to grow at a faster pace. Using full mode, the blockchain size will probably be near or over 100GB. Using light mode, the blockchain size will be under 1GB.