A virtual machine operating system for communication between first and second applications which execute in different user portions of the virtual machine operating system and use Internet Protocol (IP). The virtual machine operating system comprises a first user portion, a second user portion and a base portion. The first user portion executes the first application and includes a first device driver for a first virtual network interface card (NIC). The second user portion executes the second application and includes a second device driver for a second virtual NIC. The base portion is shared by the first and second user portions and includes the first and second virtual NICs. The base portion maintains a table of IP addresses by which each device driver addresses its respective NIC and other, corresponding addresses by which the base portion addresses the virtual NIC. The first device driver is programmed to receive an IP datagram from the first application and pass it to the first NIC using IP. The datagram includes an IP address of the second virtual NIC and an indication that the second application should receive the datagram. The base portion is programmed to determine the other address of the second NIC based on the table and transfer the datagram to a storage location associated with the second virtual NIC or the second device driver.