Consult local area network (LAN) of the problem of computer to access the network at the same time

A local area network (LAN) only one public IP is 200 PCS, each computer process running 350 access to the network at the same time, this within the local area network (LAN) process running 70000 access the network at the same time,
Because in only one public IP network, has a total of 65535 the network port regardless (reserved ports) of the system, the process of how to map all the 70000? There are (70000-65535), a process how to map? Don't use the TCP/IP protocol in the special field?