A network interface device is provided. The network interface device is connected to a computer and performs communications via a network includes a first management unit that identifies a communication connection by a port number, and manages a communication connection state of each port by a context that is stored in a storage unit and is associated with a port number, a second management unit that manages a storage state of the context, and a control unit that refers to the context, and performs an exemplary operation to establish a communication connection and an exemplary operation to cut off a communication connection between ports.