msg = "min relay fee not met, 0 < 226 (code 66)";

[Maochengfag]

I am doing BTC transaction , use BTCTransaction class I just setFee:like this:
BTCTransaction *tx = [[BTCTransaction alloc] init];
long gas = [self caculateFee:fee andAmount:amount andUtxos:txouts];
tx.fee = gas;

• (long)caculateFee:(NSString *)feeRate andAmount: (long)amount andUtxos:(NSArray )utxos{
  long utxoAmount = 0L;
  long utxoSize = 0L;
  long fee = 0L;
  for (BTCTransactionOutput txout in utxos) {
  utxoSize++;
  if(utxoAmount >= (amount + fee)){
  break;
  }else{
  utxoAmount += txout.value;
  fee = (utxoSize * 148 + 342+10) [feeRate longLongValue];
  }
  }
  return fee;
  }

[Maochengfag]

get the feeRate from https://bitcoinfees.earn.com/api/v1/fees/recommended