​​https://github.com/jzplp/Computer-Network-A-Top-Down-Approach-Answer​​

"""
UDP Socket的客户端
环境 python3
"""

from socket import *

serverName = '49.52.10.72'
serverPort = 12000
clientSocket = socket(AF_INET, SOCK_DGRAM)
# python3 改动
message = input("Input lowercase sentence:")
# python3 改动 socket要求byte类型数据
clientSocket.sendto(message.encode(), (serverName, serverPort))
modifiedMessage ,serverAddress = clientSocket.recvfrom(2048)
# python3 改动
print(modifiedMessage)

clientSocket.close()

"""
UDP Socket的服务器端
环境 python3
"""

from socket import *

serverPort = 12000
serverSocket = socket(AF_INET, SOCK_DGRAM)
serverSocket.bind(("", serverPort))
# python3 改动
print("The server is ready to receive")
while True:
    message, clientAddress = serverSocket.recvfrom(2048)
    modifiedMessage = message.upper()
    serverSocket.sendto(modifiedMessage, clientAddress)