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I want to implement a feature in which users will send ether to wallet address(0x123) and on successful deposit, it needs to automatically transfer to my cold wallet(0x983).

I can able to achieve this features with the help of smart contract but how to achieve this with an only wallet address without including smart contracts?

  • Apart from smart contracts, an easier way might be writing a script that calls web3 to monitor the balance, calculates the transfer amount (minus gas cost), and sends out the transfer transaction. – Linmao Song Apr 17 '18 at 10:47
  • How to monitor the balance of an address continuously using web3? – Karthikeyan Thangavel Apr 18 '18 at 5:18
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You can't. Wallets do not include functionality without smart contracts. I also don't see any reason why not to include smart contracts.

  • In crypto exchanges, we will deposit the ether or bitcoin in wallet address after successful deposit it will be transferred to the cold wallet of the exchange. I want to achieve the same. – Karthikeyan Thangavel Apr 18 '18 at 5:18
  • That's not functionality which exists within the wallets. It's all done outside the blockchain - unless there's a smart contract. So whenever some system detects a payment to a wallet, it gets transferred to another (cold) wallet. This is all speculative of course, exchanges don't really share details about how their systems work. – Lauri Peltonen Apr 18 '18 at 5:49
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Following discussions in the comments, I happened to have written a bash test script that does almost exact the same. Note this is a quick hack and it has the following issues

  • it is very unsafe (e.g. it leaves the personal accounts unlocked forever). I ran it for testing only, thus no issue for me. But please don't use in production without modifications.
  • The TO_ADDR must not be managed by geth (i.e. not among results of "geth account list"), otherwise it will be a dead loop. Again, it was a quick hack.
  • No performance consideration at all: a silly loop that does the check every 60 seconds.

Code:

GETH=<your geth path>
TO_ADDR=<destination addr>
for ADDR in $(${GETH} account list | grep -o -e'\{[^}]\+\}' | tr -d '}' | tr -d '{');do
    echo "unlocking '$ADDR'"
    echo "web3.personal.unlockAccount('$ADDR', '<your password>', null);" | ${GETH} attach http://localhost:8545
done

SRC=$(cat <<EOF
addrs = web3.eth.accounts;
to_addr = '$TO_ADDR';
gasPrc=web3.eth.gasPrice;
cost = 21000 * gasPrc;
for (i = 0; i < addrs.length; i++) {
    balance = web3.eth.getBalance(addrs[i]);
    send_val = balance - cost;
    if (send_val > 0) {
        val=web3.fromWei(send_val, "ether");
        web3.eth.sendTransaction({from: addrs[i], to: to_addr, value: web3.toWei(val, "ether"), gasPrice: gasPrc, gas: 21000});
        console.log("Transferring ", web3.toWei(val, "ether"), " wei from ", addrs[i], " to ", to_addr, " gas price ", gasPrc);
    } else {
        console.log("Cannot Transfer ", send_val, " wei from ", addrs[i], " to ", to_addr);
    }
}
EOF
)

while true; do
    if echo "${SRC}" | ${GETH} attach http://localhost:8545 | tee monitor.log | grep -e'Transferring ';then
        date | mail -s 'ether automatically transferred' <your email>
    fi
    sleep 60
done

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