You can't go "into" a computer. Certain programs "listen" on certain ports. If you would read the other posts more carefully you would see that. The lists that were provided show what services are usually listening on what port. It's not set in stone, it's just usually done that way. The point is, if a port is open, you need the proper client to connect. Telnet will not always work. It is NOT possible to connect directly to the persons computer via telnet and see an exact copy of their screen, data, etc. as you might expect. All you really do is connect to software programs via telnet, not the actual OS itself.