Correct me if I am wrong, but I thing waiting 48-72 hours is sometimes not necessary.
If you send transaction with very low or no fees it will not propagate in the network very well. It might even get stuck after being announced to a few nodes. If you send coins again with the fee and
use only the nodes that has not received your first low-fee transaction then you do not have to wait more than several minutes.
Using only uninformed nodes should not be difficult as this will be majority of network (your low-fee transaction is stuck only on several nodes.) I think you are right but i really want to know how to use nodes that has not received your first low-fee transaction because i sent 0.01btc from blockcain.info with 0 fee and it wasn't refunding those coins after 24hours so i decided to double-spend on my bitcoin qt 0.8.6 while it was synchronizing(about 20hours behind or so) and no active conections to the network i sent those coins and then i checked the tranasctions id on blockchain.info/tx and other blockchain explorers it sayed that tranasction dose not exist what could be wrong and why and why does this happens?
It is difficult to choose nodes manually. I think it is actually possible with some low-level approach. (Probing nodes by IP, accumulating more nodes addresses, requesting specific txids form nodes, connecting selectively to such nodes that do not know about previous transaction.) But I do not know if you have to modify and recompile your client or if it can be done by RPC calls. It is quite difficult both ways.
What I actually meant was not to try this manually, but hope that your low-fee transaction is either:
- too low fee and thus unpropagated and thus it is only matter of time and trying to double spend
- reasonable fee and thus well propagated and it is only matter of time when someone will include it
(so it should work automatically)
Unfortunately in this case, blockchain.info has some very well connected nodes and it sends transaction to big part of the network. So you can not double spend, because low-fee transaction is both of above :-/. Both well propagated (due to blockchain.info
initial propagation is always well) and too low fee (that is why it does not propagate further and why it is not included by miner). When you try to double-spend, all nodes you connect to probably already know about prior low-fee transactions.
I think, you can only wait and if AFTER rescan you will not see your previous (unconfirmed) transaction, you have chance to double spend. Or maybe the transaction will get included in low-fee variant after all. But, again, you have to wait :-/.
