Network Basics (3) 01-Basic Concepts of Networks - Protocols, Host Addresses, Paths and Parameters of URL Addresses & 127.0.0.1 Local Loopback Address & View URL IP Address and Access Ping Space + URL

Network Fundamentals (3) 01-Basic Concepts of Network - Protocol, Host Address, Path and Parameters & 127.0.0.1 Local Loopback Address & ViewURL IP address and access the ping space + URL & netstat -anb to view the port occupied by the machine

4. Basic Concepts of Networking

4.1 URL composition

URL (Uniform Resource Locator), Uniform Resource Locator, generally speaking, it means the complete access address of a web page in the network, it has a certain format: protocol://host address[:port]/path?querystring#anchor

• Protocol
  • http
  • https
• Host address, the address of the website server
  • IP address
  • Domain Name
• Port
  • http request, default port 80
  • https request, default port 443
  • MySQL default port 3306
  • When visiting a web page, default port can be omitted
• path
  • Resources on server folder (html/css/images/js/interface)
• parameter (query string)
  The part after
  • ? is in the form of a key-value pair

Example: http://itcast.cn:80/schools/students?id=18&name=zs#photo

URL role: marking resources on the network

4.2 IP address

Internet Protocol Address

• The function is to identify the address of a network device (computer, mobile phone, TV) in a specific network.
• The address of the device in a certain network, the most common format at present: [0-255].[0-255].[0-255].[0-255] isConsists of four numbers 0-255.
• In the same network, the IP of the computer is not allowed to be the same, it is all unique
• 127.0.0.1 is the local loopback address, which can always access your computer

4.2.1 Single Network Scenario

Under a single local area network, the structure is very simple, that is, the network device (gateway) we connect assigns us an address, and within this range we can all find our address through this addressthis device.

If the device is not connected to any network, we will have a local loopback address 127.0.0.1

4.2.2 Multiple network scenarios

But when a device is on multiple networks at the same time (for example, a wired network card and a wireless network card are connected at the same time), it will become a little more complicated:

View the IP address of the URL

Use the shortcut key win+r to open the run window, and enter cmd to open the command prompt window.Then enter ping www.baidu.com to check the port number opened by the machine.

ping www.baidu.com // ping space + URL

Effect - query URL ip

Access Baidu via ip

4.3 Domain Name

Because IP addresses are composed of irregular numbers, it is difficult to be remembered and not conducive to wide dissemination, so some people come up with a name (alias) for IP.

Domain names cost money to register

The purchased domain name needs to be resolved to your web server, that is, let it correspond to the server IP

4.3.1 TLD (understand)

.com: Commercial Organizations
.cn: China Country/Region Domain Names .hk,
.gov: Government Websites.
.org: Agency.
.edu: Educational website.
.net: Internet service provider.
.mil: Military.

4.3.2 Special Domain Names

localhost means the local host, corresponding to 127.0.0.1.This is a reserved domain name mainly used for local testing.

4.4 port

The computer itself is a closed environment, like a building. If there is a need for data communication, there must be a door. This door is called a port in terminology. Each port has a number, and each computer has only 65536ports (0-65535).

Generally we call the process of "occupying the door" called monitoring

The function of the port number is to identify a software in the computer and distinguish each software in the computer

Can be run from the command line:

The
• netstat -an command monitors the port usage of the machine, and only briefly displays the ports used by the machine
The
• netstat -anb command monitors the port usage of the machine, including displaying the program that occupies the port

When requesting network resources, the default port can be omitted

Reference link:

• https://baike.baidu.com/item/%E6%9C%8D%E5%8A%A1%E5%99%A8%E7%AB%AF%E5%8F%A3li>
• https://baike.baidu.com/item/%E7%AB%AF%E5%8F%A3
• http default port 80
• https default port is 443
• mysql The default port is 3306