Hosts with IP addresses can provide many services, such as Web services, FTP services, SMTP services and so on. These services can be completely realized through 1 IP address. So, how does the host distinguish different network services? Obviously, you can't just rely on ip addresses, because IP addresses and network services have a one-to-many relationship. In fact, different services are distinguished by "IP address+port number". ?

It should be noted that the ports do not correspond. For example, when your computer accesses the WWW server as a client, the WWW server uses "80" port to communicate with your computer, but your computer may use "3457".

Sample port. ?

According to the corresponding protocol type, there are two kinds of ports: TCP port and UDP port. Because TCP and UDP are independent, their respective port numbers are also independent of each other. For example, TCP has 235 ports, and UDP can also have 235 ports. There is no conflict between them.