1. A data processing system supporting a network interface device for connection to a network, the data processing system comprising: a plurality of sets of one or more data processing cores configured to receive process data received from the network, via the network interface device; and an operating system arranged to support at least one socket configured to accept said receive processed data, the data belonging to one of a plurality of data flows; wherein at least one socket is configured to have a plurality of queues, each queue of the plurality of queues dedicated to a respective one of the sets of data processing cores, a particular one of the sets of data processing cores including a processing core which receive processed said data of said one of the data flows, wherein state associated with said one data flow is provided in one of the queues dedicated to the particular set of data processing cores; and wherein an application thread executing at a particular processing core of the data processing system invokes an operation on the socket using state provided in a queue for the set of processing cores that includes the particular processing core.