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preface
In our daily life, the Network is everywhere, no matter we use mobile phones or computers, can not leave the support of the network. The Internet connects us to all parts of the world, shortens the distance between people, and enjoys the ocean of Internet information at any time.
Not only do we use the Internet for the convenience we bring, but we also need to think about the following questions:
How does the network work?
Let’s go to the computer network
Python network library
Python, as one of the high-level languages, also supports modules related to network programming.
- Python’s built-in libraries provide urllib and Request modules
- Python also supports a third module: Selenium, AIoHTTP, phantomJS
TCP/IP network model
👉 OSI seven-layer model
| The name of the | instructions |
|---|---|
| The application layer | Provides an interface to a network service for a network program |
| The presentation layer | Transform upper-level data or information to ensure that the application can understand it |
| The session layer | Responsible for establishing, managing, and terminating sessions between processes |
| The transport layer | Responsible for segmenting the upper layer data to provide end-to-end transmission, representing the device gateway |
| The network layer | Is responsible for routing data packets between subnets on behalf of the device router |
| Data link layer | Package the data at the network layer, or parse the physical layer data to the network layer. Representative Device switch |
| The physical layer | The data is parsed to the data link layer, or the data transmitted by the data link layer is packaged and transmitted to the hardware device for transmission. Represents the device network card and hub |
👉TCP/IP network model has four layers:
| The name of the | agreement |
|---|---|
| The application layer | SMTP, FTP, DNS, SNMP, NFS, HTTP, TELNET |
| The transport layer | TCP, UDP |
| The network layer | ICMP, IGMP, IP, ARP, RARP |
| Network interface layer | LAN, WAN, MAN |
URL
👉 Uniform Resource Locator (URL) object represents Uniform Resource Locator.
Page request mode
👉 can be divided into Request and Response during network Request
- Request: Sends requests to the server
- Response: After receiving the request from the client, the server verifies the validity of the request and returns it to the client based on the query of the request content.
💡 The network requester is GET and POST
- GET: The most common request mode. The transmitted data is displayed in the URL and the data transfer size is limited
- POST: indicates that the URL does not display the transmitted data. The URL is sent as a form to query and modify the information
🔔GET and POST highlights
- Both the GET and POST network layers use TCP
- GET generates only one TCP packet in a network request, whereas POST generates two TCP packets in the entire network
GET Sends the HEADER and data to the server once in a request. POST sends the HEADER to the server first. After the server returns 100, it sends more data to the server, returning 200.
HTTP and HTTPS
HTTP: hypertext transfer protocol. It is an application-layer protocol used to transfer information between web browsers and servers
HTTPS: a hypertext transfer security protocol that uses THE SSL/TSL encryption technology and HTTP to secure network data transmission
Differences between HTTP and HTTPS:
- The default HTTP port is TCP port 80, and HTTPS port is TCP port 443
- HTTP data is transmitted in plain text. SLL encryption is required before HTTPS data is transmitted
- The HTTP page responds faster than HTTPS. HTTP requires three TCP packets, and HTTPS requires 12 TCP packets for data transmission
The HTTP status code
| Status code | instructions |
|---|---|
| 2XX | successful |
| 200 | The request is successful |
| 201 | Immediately following the POST command |
| 202 | Received for processing, but processing is incomplete |
| 203 | Return partial information |
| 204 | No response, request received, but no information to return |
| 3xx | redirect |
| 300 | The documentation for the Multiple Choices customer request can be found in Multiple locations |
| 301 | Moved – The requested data has a new location and the change is permanent |
| 302 | Found – Requested data temporarily has a different URL. |
| 304 | Unmodified – The document is not modified as expected. |
| 4xx | An error occurred in the client |
| 400 | Incorrect request – There is a syntax problem in the request |
| 401 | Unauthorized – Unauthorized client access to data |
| 403 | Forbid – Access is not required even if authorized |
| 5xx | An error occurred in the server |
| 500 | Internal error – The server was unable to complete the request due to unexpected circumstances |
| 502 | Error Gateway – The server received an invalid response from the upstream server |
| 505 | The HTTP version is not supported |
Commonly used tools
Postman is usually the one we use most during debugging
The Postman tool is powerful enough not only to simulate interface requests for various protocols, but also to support script runs such as batch triggering
Postman official website documentation tutorial
conclusion
In this installment, we’ll take a look at the Python modules that support network programming and learn the basics of computing networks
Next we will start to learn Python network programming related module methods
That’s the content of this episode. Please give us your thumbs up and comments. See you next time