Official introduction: Internet access permanent free intranet port mapping, intranet penetration software, easy access to connect to the intranet, 100% penetration of the intranet, no router, no public network ip, no fixed ip, no dynamic domain name, users can add multiple maps for free, suitable for companies, community broadband, rental houses, campus networks, Internet cafes, education networks, and other complex network structures, Use in a strictly restricted environment. Usage Note: Select an appropriate mapping type to classify common services Applications using single port mapping (services that only listen to one port): mssql, mysql, oracle, svn, 3389, vnc, ssh, My World, etc. 2 Applications that use full port mapping (listen to services on multiple ports): ftp