On the opposite side, if a call writer finds a sufficiently attractive newBid, they can sell this call to the long. Similarly, they must confirm all of the same parameters and details match what they are aiming to sell. The smart contract checks that the short has sufficient balance and then pulls the tokens into the smart contract for escrow. In addition, given the premium was already sitting in escrow with the smart contract, that price is now delivered out to the call short (less any fees). Thus the call is now open, and the call.Short is assigned to the new call short (msg.sender), and similarly it is no longer tradeable.