4-1 port scanning technology

Basic introduction to ports

“ port ” It's English port Free translation of , It can be regarded as the outlet of communication between the equipment and the outside world . Ports can be divided into virtual ports and physical ports , The virtual port refers to the internal port of the computer , invisible . For example, in a computer 80 port 、21 port 、23 Port, etc . The physical port is something we can see everyday , For example, a socket is a port

One has IP The host of the address can provide many services , such as web service 、FTP service 、SMTP Service etc. , These services are fully accessible through 1 individual IP Address to achieve . that , How do hosts distinguish between different network services ？ Obviously, we can't just rely on IP Address , because IP The relationship between address and network service is one to many . In fact, by “IP Address + Port number ” To distinguish between different services .

therefore , An open port represents a service provided , Different services have different port numbers , So test the service , First, determine whether the currently tested machine opens the corresponding port number

Port scan tool -Nmap

There are ports , Category is tcp, state ,OPEN Open , Each port , On behalf of his open service , And his mac Address , Time spent

Port scan tool -Dmitry

dmitry You can query a lot of information , Especially for WEB Server queries ,whois Information , Return the domain name information

dmitry When writing this software , Common ports are set , Then detect , Those big ports , There was no detection ,nmap Is a powerful port scanner ,dmitry Port scanning is only a part of all its functions

Port scan tool -netcat

The more ports scanned , The slower you scan