Catalog

The Internet foundation 1

Internet Protocol

  The link layer

1. Access point mode

2. Wireless terminal mode

3. Mixed mode

  The network layer

 IP Address

gateway

  Subnet mask

  The Internet foundation 2

TCP agreement

  characteristic ： steady

  Application field

UDP agreement

   characteristic ： fast

  application layer （HTTP agreement ）

 HTTP Request example

 HTTP Response example

  More knowledge , Look at this.

The Internet foundation 1

Internet Protocol

  In order to enable network devices to communicate correctly , Use language that can be understood by each other , We call it an agreement

The Internet uses --TCP/IP agreement Protocol group

  The link layer

The main function is to realize the The physical connection , for instance , What we use WIFI It is a single kind of link layer protocol  

 ESP8266 utilize WIFI When networking Three Working mode

1. Access point mode

ESP8266 Launch to the outside WiFi The signal Be able to build a WIFI The Internet

2. Wireless terminal mode

By connecting WiFi The router realizes the communication between the Internet

3. Mixed mode

  The network layer

 IP Address

： Usually we say IP Most addresses refer to those connected to the Internet IP Address , We know that every computer connected to the Internet will be assigned a IP,IP The address is provided by the network provider , You can also know the general direction according to its address ,

Key studies IPV4

  In the picture 3 All devices are connected to wifi When it comes to routers ,WIFI The router will allocate Independent Of IP Address

  For example, when the mobile phone sends data packets , Must indicate what happened IP Address , Can be sent to

This is on my own computer At present LAN Upper IP Address （ stay win+r Output cmd, play ipconfig Inquire about ）

gateway

wifi The router is in this LAN gateway

        The above IP The addresses are all in the LAN IP Address ,

         When in China Unicom server or other time , Meeting Assign other Of IP Address

  When the computer accesses the website server , The process of sending packets

  Subnet mask

  The Internet foundation 2

TCP agreement

  characteristic ： steady

        · Guarantee all Data can be received by the receiving end        （ Not at all 100% Can be accepted , Just want to be more stable ）

        · The data transmission sequence will not be disturbed

        · If the transmission data is damaged, resend the damaged data

shortcoming ： Slow speed

  Application field

         · E-mail

        · File transfer

       .....

UDP agreement

   characteristic ： fast

        ·UDP Than TCP Fast

        · It is not guaranteed that all data can be received by the receiving end （ It's all relative ）

         · Once the data is damaged , Will be directly abandoned

        · If there is data corruption, it will not resend the damaged data

  application layer （HTTP agreement ）

  give an example ：

Enter web address in browser , Press enter , The browser will convert it into a request Data packets , Send to the Internet

Then send it to the website server

After the website server receives it , Generate a response （ It is also a packet ）, Send it to my computer through the Internet

Finally, the corresponding interface is displayed on the browser of the computer

 HTTP Request example

  If sending a message GET become POST   

 HTTP Response example

  or

  When we use the development board , It's not the computer that sends the request and receives the response , Instead, use the development board directly

  More knowledge , Look at this.

The first 2 Chapter Internet knowledge base – Taiji maker