pythonnet-Network Programming (1)

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Python network programming has a lot of difficulties, but also easy to forget, recently I will be issued a system, complete pythonnet knowledge of the blog, while reviewing while sharing, interested can pay attention to me.

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Network programming

Purpose: Transfer of data

ISO (International Organization for Standardization)

OSI seven-layer model-----> Standardized process for network communication

Application layer: Provision of User services, specific content specified by the program

Presentation layer: Provides encryption and compression optimizations for data

Session Layer: Make sure to set up the application link and select the Transport service

Transport layer: Provides data transfer services for flow control

Network layer: Route selection, Network interconnection

Link Layer: Provides link switching, sending of specific messages

Physical layer: Physical hardware, interfaces, network card provisions

Can be divided into four-layer models

Four-layer model

Application Layer

Transport Layer

Network layer

Physical link Layer

Divided into five-tier model (TCP/IP model)

Application layer (Application Layer presentation layer session layer)

Transport Layer

Network layer

Link Layer

Physical Layer

The advantages of the OSI model: separating functions, reducing coupling in network transmission, and making the development process clearer

Each part of its duties.

High aggregation: Each module functions as single as possible, does not have multiple function doping

Low coupling: Minimizing the correlation between each module

Network protocol: A requirement that all parties to the agreement must comply with in network communication. such as what connection to establish, how the message structure is parsed, etc.

Application layer: TFTP HTTP DNS SMTP

Transport Layer: TCP UDP

Network layer: IP

Physical Layer: IEEE

Network-related concepts

Network host: Determine a host on the network

Local use: "localhost" 127.0.0.1

Network address: "0.0.0.0" "172.60.50.54" (Native network IP)

View native IP address: ifconfig (Linux)

ipconfig (Windows)

Ipython3 into interactive mode

Obtaining a matching IP by computer name

Socket.gethostbyname ("localhost")

"127.0.0.1"

Get the computer name of the machine

Socket.gethostname ()

"XXXX"

IP Address

Determine the address of a host on the network

IPV4: Dotted decimal

ipv6:128 bit

Network Connectivity Test

Ping 172.60.50.182

Special IP

127.0.0.1 Local Test IP

0.0.0.0 automatic use of locally available NIC IP

192.168.1.0 represents the current network segment

192.168.1.1 is usually the gateway address

192.168.1.255 Broadcast Address

IP address converted to hexadecimal expression

Socket.inet_aton (' 192.168.1.2 ')

B ' \xc0\xa8\x01\x02 '

Domain: The name of the network server address on the network

Port number: Port number is part of the address, in a system each network application listens to different ports, to obtain the corresponding port to pass the information

Value range: 1----65535
1-255 some common ports (well-known program occupancy)
256--1023 System Port
1024--65535 personal port >10000

Transport Layer Services

Connection-oriented transport service---"TCP protocol

Transmission characteristics:

Reliable data transfer
Reliability: Data in transit, no out of sequence error-free no loss no duplication

Connection and disconnection required before and after data transfer

Three-time handshake: the process of establishing a connection in a connection-oriented transport service

1. The client sends a connection request to the server
2. The server accepts a request for confirmation and returns a confirmation message.
3. Client receives server reply final confirmation connection

Four waves: The process of disconnecting from a connection-oriented transport service station

1. The active party sends a message informing the passive party to disconnect
2. Passive response message, indicating that the request has been received, ready to disconnect
3. The passive party sends the message again, indicating that it is ready for processing and can disconnect
4. Unsolicited send acknowledgement message, disconnect

Application: Suitable for transmission of large content or files, network is good, need to ensure the transmission reliability of the situation
e.g. upload and download of chat information files, mail processing
Web Access

UDP protocol for non-connected transport service---"

Transmission characteristics:
No guarantee of transmission reliability
No connection and disconnection process
The first of the data is more free

Application: Network conditions may result in packet loss, low transmission reliability requirements

e.g.: Network video, group chat, broadcast, etc.

Socket Socket Programming

Purpose: The socket programming interface provided by programming language makes it easier to complete TCP and UDP-based programming

Sockets: A programmatic means of accomplishing these goals

Socket category

Streaming Sockets (SOCK_STREAM): Transport-Layer TCP-based protocol communication
Transport-Flow sockets for connection-reliable transport of TCP

Datagram Sockets (SOCK_DGRAM): Transport layer transmission based on UDP protocol
Transmit datagram sockets for non-connected unreliable transport UDP

Underlying sockets (Sock_ram): Accessing the underlying Protocol sockets

Service side of TCP

Import socket

1. Creating sockets

Socket.socket (sock_family = Af_inet,
Sock_type = Sock_stream,
Proto = 0)
Features: Creating sockets
Parameter: sock_family address family type af_inet IPv4 network communication
Sock_type Socket Type Sock_stream streaming
Sock_dgram Data Report
Proto typically 0 selected sub-protocol type
Return value: Returns the Socket object

2. Binding Address

Sockfd.bind (addr)
Function: Bind address
Parameters: Addr---"Tuple (ip,port) (' 0.0.0.0 ', 1234)

3. Setting up the listener socket

Sockfd.listen (N)
Function: Set socket to listen socket, create listening queue
Parameters: Listening Queue size

* One listener socket can connect multiple clients

4. Waiting for client connections to be accepted

CONNFD,ADDR = Sockfd.accept ()
Features: Blocking waits for processing client connections
Return value: CONNFD new socket for communicating with clients
Addr the address of the connected client (Ip,port)

* Blocking function: When the program runs to the blocking function position, if a condition is not reached then the program is suspended, knowing that the condition is reached to end blocking

5. Sending and receiving messages

data = CONNFD.RECV (buffersize)
Function: Accept Message
Parameter: The size byte of an accepted message at a time
Return value: Returns the accepted content

n = connfd.send (data)
Function: Send Message
Parameters: What to send (bytes format)
Return value: Returns the number of bytes actually sent

6. Close the socket

Sockfd.close ()

* Telnet IP Port

Client

1. Create socket (same as service end socket type)
2. Initiating a connection

Connect (addr)
Function: Initiate a connection to the server
Parameters: Service-side address tuple

3. Sending and receiving messages
4. Close the socket

Here's the code, which is the client code

This is the service-side code:

OK, this section ends, small partners can use Pycharm (Community edition free) run try, we see next time!

pythonnet-Network Programming (1)