现在需要客户端和服务端通信，服务端主动给客户端发信息

服务端

import socket
import time
BUF_SIZE = 1024
host = '0.0.0.0'
port = 9998

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind((host, port))
server.listen(1) #接收的连接数
client, address = server.accept() #因为设置了接收连接数为1，所以不需要放在循环中接收
while True: #循环收发数据包，长连接
    #data = client.recv(BUF_SIZE)
    #print(data.decode()) #python3 要使用decode
    client.send('keepalive\r\n'.encode())
    time.sleep(60)
    # client.close() #连接不断开，长连接

客户端

import socket
import datetime

print(datetime.datetime.now())

host = 'barcode.ydqzj.cn'
port = 9998
BUF_SIZE = 1024
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1) #在客户端开启心跳维护
client.connect((host, port))
while True:
    #client.send('hello world\r\n'.encode())
    #print('send data')
    data = client.recv(BUF_SIZE)
    print(data.decode())
    #time.sleep(5) #如果想验证长时间没发数据，SOCKET连接会不会断开，则可以设置时间长一点