The python Network Programming (UDP socket based communication protocol)

8.5 socket communication based on UDP

UDP protocol: Datagram Protocol Features: no connection, out of the corresponding closing a first end of which will not be given start advantages: high transmission efficiency, but the amount of data transmitted most effective 500bytes

Disadvantages: unreliable: transmitting data without acknowledgment, easy loss

udp server

SS = socket 1 ()    # create a server socket 
2 ss.bind ()        # bind server socket 
3 inf_loop:        # server infinite loop 
4 cs = ss.recvfrom () / ss.sendto () # Dialogue (receive and transmit) 
. 5 ss.close ()                          # close server socket

udp client

socket = cs ()    # create a client socket 
comm_loop:       # communication cycle 
    cs.sendto () / cs.recvfrom ()    # Dialogue (send / receive) 
cs.close ()                       # close the client socket

8.6 client and server operations (based on UDP)

Server:

Import Socket
                    # address family, based on the network # Datagram Protocol      
Server = socket.socket (socket.AF_INET, socket.SOCK_DGRAM) 
server.bind (( ' 127.0.0.1 ' , 8080))                  # the address bound to the socket ( 0-65535) 0-1024 to the system used in 
the while True: 
    client_data, client_addr = server.recvfrom (1,024) # received message, a maximum limit is 1024 Print (client_data.decode ( ' UTF-. 8 ' )) 
    MSG = INPUT ( ' reply S%:% S >>>: ' % (client_addr [0], client_addr [. 1 ])) 
    server.sendto (msg.encode ( '
    utf-8'),client_addr)

Client:

import socket
​
client=socket.socket(socket.AF_INET,socket.SOCK_DGRAM) # 数据报协议
​
while True:
    msg=input('>>>: ').strip()
    client.sendto(msg.encode('utf-8'),('127.0.0.1',8080))
    res,server_addr=client.recvfrom(1024)             #收消息
    print(res.decode('utf-8'))

8.7 Datagram Protocol does not stick package problem

udp The recvfrom is blocked, a recvfrom (x) must only sendinto (y), ended all x bytes of data even if completed, if y> x data is lost, which means that will not stick udp packet, but it will lose the data, unreliable

Each have a UDP packet (information source address and port) message header, so the receiving end to it, it is easy to distinguish the process. That message is a message-oriented communication protected boundaries.

Server:

import socket
​
server=socket.socket(socket.AF_INET,socket.SOCK_DGRAM) # 数据报协议
server.bind(('127.0.0.1',8080))
​
res1,client_addr=server.recvfrom(1)             #b'h'
print(res1)
​
res2,client_addr=server.recvfrom(2)             #b'wo'
print(res2)
​
res3,client_addr=server.recvfrom(3)             #b'ego'
print(res3)

Client:

Import Socket 
Client = socket.socket (socket.AF_INET, socket.SOCK_DGRAM) # datagram protocol 

client.sendto (B ' Hello ' , ( ' 127.0.0.1 ' , 8080 )) 
client.sendto (B ' World ' , ( ' 127.0.0.1 ' , 8080 )) 
client.sendto (B ' Egon ' , ( ' 127.0.0.1 ' , 8080))