A local host data processing system operating under the control of a local host operating system includes components of multiple emulating hosted operating systems. The host operating system further include a TCP/IP network protocol stack which couples to the communications facilities of the host system connected to a local area network for communicating with a number of remote host systems. Host and hosted operating systems share the same TCP/IP network protocol stack. A virtual network mechanism is configured within the local host system to be operatively coupled to the host network protocol stack and provide access to well-known port application programs. When so configured, the mechanism functions as another LAN to which multiple virtual host systems are attached for executing applications under control of the emulating hosted operating systems. The mechanism transforms the well-known port identifier of each inbound packet into a non-well-known port identifier in addition to other station address identifier fields. It then redirects the transformed packet back to the IP layer of the stack for transfer to the appropriate well-known port application program being run by the hosted operating system of the particular virtual host system. The mechanism reverses this operation for each reply packet which it redirects back to the IP layer for forwarding to the remote system. This eliminates the need to specify additional protocol stacks and to provide additional communication hardware facilities for handling multiple instances of well-known port applications programs running on the different virtual host/multiple hosted operating systems.