[Ethereum] Connecting to hosted web3 provider from NodeJS backend

Infura currently doesn't support WebSockets (required for events using Web3 v1, otherwise you get the error "The current provider doesn't support subscriptions" when using infura as HttpProvider), so what you have to do is run a local geth node that connects and syncs to the network.

Here we enable the websocket flag and allow any origin to connect to the local geth node that is syncing with the rinkeby testnet:

geth --rinkeby --ws --wsport=8546 --wsorigins="*" --datadir=$HOME/.rinkeby --cache=512 --rpc --rpcapi="personal,eth,network" --rpcport=8545 --fast --bootnodes=enode://a24ac7c5484ef4ed0c5eb2d36620ba4e4aa13b8c84684e1b4aab0cebea2ae45cb4d375b77eab56516d34bfbd3c1a833fc51296ff084b770b94fb9028c4d25ccf@52.169.42.101:30303

To check the syncing status:

geth attach ipc:$HOME/.rinkeby/geth.ipc
> eth.syncing

Once it's done syncing you can connect using the WebsocketProvider:

const web3 = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'))

You should now be able to receive events:

myContract.events.allEvents((error, event) => {
  if (error) {
    console.error(error)
    return false
  }

  console.log(event)
})

Tested this with geth v1.6.5 and web3 v1.0.0.

Update Oct 11, 2017:

Infura is experimenting with websocket support. You can ask for beta access in this github issue thread:

https://github.com/INFURA/infura/issues/29

let send_add = send_public_address;

let recv_add = rec_public_address;

let transfer_amount = web3.toWei(data.amount, 'ether');

let nonce = web3.toHex(web3.eth.getTransactionCount(send_public_address));

var private_key = privatekey_sender.slice(2);

let gas = web3.toHex(data.gas_limit);

let gasPrice = web3.toHex(data.gas_price);

var rawTx = {

        from: send_add,

        nonce: nonce,

        gasLimit: gas,

        gasPrice: gasPrice,

        value: web3.toHex(transfer_amount),

        to: recv_add,

    };

var transaction = new tx(rawTx);

var txData = new Buffer(private_key, 'hex');

transaction.sign(txData);

var serializedTx = transaction.serialize().toString('hex');

web3.eth.sendRawTransaction('0x' + serializedTx, function (err, txHash) {

  if (txHash) {

            next(null, txHash);

        }

        else if (err && err.message) {

            next(err.message, null);

        }

        else {

            next('Unable to sendRawTransaction', null);

        }

    });