Specfically, how does an EMV device talk with the card issuer? -

when doing emv online transaction (arqc), emv device needs communicate issuer (or gateway) approval/denial. writing pos software , need support emv, need support interaction. can't seem answer is, part of emv specification emv device communicate directly issuer, on internet? or need looking sort of send function in device's api?

i know question directed @ hardware manufacturer's design, have read few api's different emv devices , non of them seem detail communication. of them have function initialize emv capabilities (with transaction amount) , callback/event when transaction completed. leads me believe need provide internet connection device , magic happen.

as followup that, see devices have usb communications (instead of ethernet). these devices (obviously) couldn't talk directly outside network. safe assume these devices going every emv transaction offline? or missing something?

as far have come understand, emv covers finer details of communication between card , reader device, gives procedure/standards followed when delivering data online. thus, once have performed local processing of card, use whichever means can find deliver info online acquirer (assuming online transaction) , communication must fulfill emv (and pci) security requirements. yes, need internet connection online transactions. part, "encode" data according financial standards , protocols , send specified acquirer/issuer, need created developer (you).