Ykhjuy

web3.eth.getTransactionCount(addressFrom).then(function(v){

    count = v;

    var amount = web3.utils.toHex(1e16);

    var rawTransaction = {"from":addressFrom, "gasPrice":web3.utils.toHex(20* 1e9),"gasLimit":web3.utils.toHex(210000),"to":contractAddress,"value":"0x0","data":contract.methods.transfer(addressTo, amount).encodeABI(),"nonce":web3.utils.toHex(count)}

    var transaction = new Tx(rawTransaction);

    transaction.sign(privKey);

    web3.eth.sendSignedTransaction('0x'+transaction.serialize().toString('hex'))

    .on('transactionHash',console.log);

});

If I send raw transaction more than once in quick, I get the known transaction error.

I got "UnhandledPromiseRejectionWarning: Error: Returned error: known transaction: 288cd7f1dc2dXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX".

Maybe something is without the 0x, but I don't know how to do that.
Thanks for helping me.

Most probably this is because when you send two raw transactions quickly, both of your transactions get the same nonce value as you are passing the transaction count of the address as nonce. So in quick sending, transaction count doesn't get updated. Hope it helps!