Python-network Programming-socket Programming

first, socket Syntax

Network Seven layer model (osi Model)

1 Physical layer-->2 Data link Layer (mac address)-->3 Network layer (ip)-->4 Transport Layer (tcp/wireless, UDP Protocol transport)-->5 session layer-->6 presentation layer-->7 application layer (http, ftp, smtp, Pop3)

socket syntax and related knowledge points:

The socket is a two-way channel for two programs to achieve data transfer. The network communication is the specific service that locates the specific target machine through ip+port, the operating system has 0-65535 ports, each port provides the service independently.

There must be two ports to build a socket: server and client

server : Passively waits for client requests to be accepted

Setup Process: 1. Create a Socket instance Sk-->sk.bind () set the network address and port number that the server can listen On-->sk.listen () start listening--

Cnn,val=sk.accepr () accepts the Client's connection-->cnn.recv () accepts Data-->cnn.send () sends Data-->close

1, establish a socket instance: socket.socket ()

1 Import Socket 2 server=socket.socket (socket.af_inet,socket. Sock_stream)

The first parameter is: address cluster

Socket.af_inet IPv4

Socket.af_inet6 IPV6

Socket.af_unix UNIX native-to-computer Communication

       

Second Parameter: socket type

Socket. Socket_stream for TCP

Socket. Socket_dgram for UDP

  Socket. sock_raw   Raw sockets, normal sockets cannot handle network messages such as icmp, igmp, and Sock_raw can; Sock_raw can also handle special IPv4 messages, and with the original sockets, the IP header can be constructed by the user through the IP_HDRINCL socket Option.

        socket.SOCK_RDM       是一种可靠的UDP形式，即保证交付数据报但不保证顺序。SOCK_RAM用来提供对原始协议的低级访问，在需要执行某些特殊操作时使用，如发送ICMP报文。SOCK_RAM通常仅限于高级用户或管理员运行的程序使用。

2. Binding address: Sk.bind

The format of address is dependent on the addressing cluster, and if it is IPV4, the address is passed in as Ganso

1 server.bind (('0.0.0.0', 8001))

3, Start listening: Sk.listen (backlog)

Start listening for incoming connections, the backlog represents the maximum number of connections that can be suspended before a connection is denied, with a backlog of up to 5

1 server.listen (5)

4. Receive the connection and return the new socket object and client address

1 cnn,client_addr=server.accept ()

CNN for the new socket object, Clinet is the client address of the connection

5. Accept and send client data

1 cnn.recv (1024x768)2 cnn.send (b'got your msg')

Client : Proactively sending requests to the server

Process: establish a socket instance C-->c.connect () connection server-->c.send () send data-->c.recv () accept Data-->c.close ()

1 ImportSocket2Client=socket.socket ()#1. Set up socket instance3Client.connect (('localhost', 8001))#2. Connection4Msg=input ('>>:')5Client.send (msg.encode ())#3. Send data6 Print('send:%s'%Msg)7Data=client.recv (1024)8 Print('receive from server:%s'%data)#4. Acceptance of data

Here's a little Exercise:

Service Side:

1 ImportSocket2Server=Socket.socket (socket.af_inet,socket. Sock_stream)3Server.bind (('127.168.0.1', 8001))4Server.listen (5)5 Print('------------start to listen--------')6  whileTrue:#when the client disconnects from the server, it prevents the error from jumping out of the second loop, but returns to the loop and re-accepts the request from the other Client.7Cnn,client_addr=server.accept ()8     Print(cnn,client_addr)9      whileTrue:Ten         Try: oneData=cnn.recv (1024)#There is a client disconnect is, recv is not connected, will error, use try to do exception handling, to prevent program termination a             Print('client:%s'%Data) -S_data=input ('Service Side:') - cnn.send (s_data.encode ()) the         exceptConnectionreseterror as E: -             Print(e) -              break

Client:

1 ImportSocket2Client=Socket.socket ()3Client.connect (('127.168.0.1', 8001))4 5  whileTrue:6Msg=input ('client:')7 client.send (msg.encode ())8     #print (' send:%s '%msg)9Data=client.recv (1024)Ten     Print('Service side:%s'%data)

Python-network Programming-socket Programming