A method for data communication in a vehicle between an in-vehicle device and a mobile device coupled with the vehicle includes transmitting, by the in-vehicle device, data via a data bus of the vehicle to an in-vehicle data communication device, a first data protocol being used for this purpose, in which an arbitration occurs. The data communication device converts the data, and the data communication device transmits the converted data via a data link to the mobile device. A second data protocol is used in the data transmission from the in-vehicle data communication device to the mobile device, in which no arbitration occurs. A data communication device by which the method of the invention may be implemented is also described.