Basic introduction of network overview

The network is a tool to help two or more parties connect together.

It is used to connect multiple parties and then communicate, that is, to transmit data from one side to the other.

In order to solve the language communication barriers between people of different races, it is now stipulated that the international common language is English, which is both a stipulation and an agreement.

This is the same as communicating with people above. Computer communication also stipulates rules, which is the protocol.

If computers all over the world want to communicate together, they need protocols. There are too many Internet protocols, so we will introduce the two most important ones now, so we call them TCP/IP protocols for short.

Let's take a look at our common protocols:

Application layer protocols: DHCP, DNS, FTP, POP3, SSH.

Transport layer protocols: TCP, UDP

Network layer protocol: IP

Data link layer: WIFI, GPRS,

Physical layer: Ethernet, modem

If a process needs to send and receive network data, it needs to have such a port for a long time. The port of each application is different, and the data will not be sent wrong.

The maximum number of ports is 65536.

Ports are marked by port numbers, which are only integers from 0 to 65535.

Some well-known port numbers are fixed.

80 is assigned to the HTTP service.

Port 2 1 is assigned to the FTP service.

Mysql port 3306

And dynamic port numbers.

It is called dynamic because it generally does not allocate a service fixedly, but dynamically.

When a system process or an application process needs network communication, it applies for a port from the host, and the host assigns an available port number for it to use.

Close the program and release the port.

Network statistical database