In network technology, ports have two meanings: one is physical ports (hardware ports, also called interfaces), such as interfaces used by ADSL modems, hubs, switches and routers to connect with other network devices, such as RJ-45 ports and SC ports; The second is logical port (software port), which generally refers to the port in TCP/IP protocol. It is an abstract software structure, including some data structures and I/O buffers. Port numbers range from 0 to 65535, such as port 80 for browsing web services, port 2 1 for FTP services and so on.