Exchange coins locally

[Merca]

Hello, people. Is it possible to exchange different coins locally instead of using an exchange service like ShapeShift? Let's say I have installed the cores of both currencies, Bitcoin and Ethereum for example with their corresponding wallets. Can't I somehow exchange between the two? I understand the networks are different but I still don't get it how those online exchange services do it that can't be done locally. If you'd like to point me into the right direction I'd also be happy because I've been looking this kind of info for hours to no avail.
Thanks a lot.

[DannyHamilton]

multi
I understand the networks are different but I still don't get it how those online exchange services do it that can't be done locally.

Exchange service has multiple wallets with coins in each wallet.  You send them one kind of coin, they send you some of their other kind of coin.  They don't "exchange between the two".

So for example, they service is running BOTH a Bitcoin wallet AND an Ethereum wallet.  When you send them some Bitcoins to exchange for Ethereum, they notice the incoming bitcoin transaction.  They do the math to figure out how many Ethereum that should be.  Then they send you the calculated amount of their Ethereum from their Etherium wallet.

Later someone else sends the service some Etherium to the service's Etherium wallet.  This other person wants some Bitcoins.  The service notices the incoming Etherium transaction. They do the math to figure out how many Bitcoins that should be. Then they send that person the calculated amount of the Bitcoins from their Bitcoin wallet. Most likely the some of the bitcoins that they are sending out are bitcoins that they recently received from you.

[Hichi]

Hello, that's not possible unfortunately. How the exchanges work is this way, they simply keep a lot of e.g. BTC and ETH in their reserve (or a portion of it) which is used for daily trading. They are not actually exchanging it themselves, the traders on the platform are the one who exchange them. The exchanges are only market makers, they faciliate the place for this exchange to happen, but in reality their job is to basically store all these assets and offer the interface for traders to exchange their stuff. There are various new solutions coming out, so you'd be happy to hear that sonner or later a decentralized exchange will appear that will make exchanging between networks very easy, some are already out there e.g. KyberNetwork, Bancor, 0x.. all these projects are trying to solve the problem you've asked about