测试的后端弄一个可以供测试的就行（比如在console依次输出1，2，3），前端要一个按钮，点击后可以跟进更新，不需要刷新，显示1，2，3。我能完成测试就采纳了。
server.py
import json, time, random
from flask import Flask, render_template
from flask import request
from flask import make_response
from gevent import pywsgi
from geventwebsocket.handler import WebSocketHandler
from threading import Thread
# 实例化产生一个Flask对象
app = Flask(__name__)
WS_LIST = []
count = 0
def get_host_ip():
# 获取本机ip
import socket
hostname = socket.gethostname()
ip = socket.gethostbyname(hostname)
if '127.0.0.1' in ip:
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
try:
s.connect(('8.8.8.8', 80))
ip = s.getsockname()[0]
finally:
s.close()
return ip
self_ip = get_host_ip()
# flask的路由是基于装饰器的
@app.route('/', methods=['GET', 'POST'])
def hello_world():
return render_template("index.html",self_ip=self_ip)
@app.route("/main")
def func():
global count
ws = request.environ.get('wsgi.websocket')
if not ws:
print('【客户端退出1】', str(ws))
return make_response("error", 404)
WS_LIST.append(ws)
print('len(WS_LIST)', len(WS_LIST)) # 客户端数量
while True:
# 等待用户发送消息，并接受
message = ws.receive()
# 关闭：message=None
if not message:
try:
print('【客户端退出2】', str(ws))
WS_LIST.remove(ws)
del ws
print('len(WS_LIST)', len(WS_LIST))
except Exception as e:
print(e)
return make_response("error", 404)
# msg = json.loads(message)
# print(msg)
for item in WS_LIST:
res = json.dumps({'data': count})
item.send(res)
if __name__ == '__main__':
def foo():
global count
while True:
time.sleep(1)
count += 1
print(count)
t1 = Thread(target=foo) # 创建线程对象
t1.start() # 启动线程
server = pywsgi.WSGIServer(('0.0.0.0', 6000), app, handler_class=WebSocketHandler)
print(f'server start http://{self_ip}:6000')
server.serve_forever()
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>text</title>
</head>
<body>
<input type="button" value="按钮" onclick="test()"/>
<div id="one"></div>
<script>
function test() {
let self_ip = '{{self_ip|safe }}'
let url = "ws://" + self_ip + ":6000/main"
console.log(url)
let ws = new WebSocket(url);
ws.onmessage = function (event) {
document.getElementById('one').innerHTML = event.data;
setTimeout(function () {
ws.send(JSON.stringify({'hello': 'world'}));
}, 1000)
};
ws.onopen = function (evt) {
console.log("Websocket open success", url);
ws.send(JSON.stringify({'hello': 'world'}));
};
ws.onclose = function (evt) {
console.log("Connection closed.", evt);
ws.close();
};
}
</script>
</body>
</html>
打开多少个客户端都没问题
Flask==1.1.1
Flask-Sockets ==0.2.1
gevent==21.8.0
gevent-websocket==0.10.1
前端：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>text</title>
</head>
<body>
<input type="button" value="按钮" onclick="test()" />
<div id="one"></div>
<script>
function test(){
let ws = new WebSocket("ws://localhost:8888/main");
ws.onmessage = function (event) {
document.getElementById('one').innerHTML = event.data;
};
}
</script>
</body>
</html>
后端：
from flask import Flask,render_template,request
from flask_sockets import Sockets
import datetime
import time
from gevent import pywsgi
from geventwebsocket.handler import WebSocketHandler
app = Flask("__name__")
app.debug = True
sockets = Sockets(app)
"""
主界面
"""
@app.route("/")
def index():
return render_template("index.html")
"""
websocket
"""
@sockets.route("/main")
def cs(ws):
if request.environ.get('wsgi.websocket'):
ws = request.environ['wsgi.websocket'] # websocket对象
x = 0
while 1:
x+=1
if not ws.closed:
try:
ws.send(str(x))
except(IndexError):
pass
time.sleep(1)
if __name__ == "__main__":
ip=('127.0.0.1',8888)
server = pywsgi.WSGIServer(ip,application=app,handler_class=WebSocketHandler)
print(ip[0]+":"+f"{ip[1]}")
server.serve_forever()
如题，实现以上功能，我知道主要有两大种思路：
轮询：轮询的原理是隔一段时间向服务器发送一个请求，这里不累述。这里主要谈一下第二种思路。
websocket进行前后端通讯：websocket是html5的新协议，基于TCP，在一次握手后，建立http连接，实现客户端与服务端全双工通信。相比较轮询机制，节约资源，不需要频繁的请求。
下面通过最精简的javaweb+mysql实例说明，只贴出关键代码。（原码放在github中，里面有本例需要的websocket-api.jar，.sql文件以及README.doc，方便理解本例）。
user.jsp:
<%@ page import="model.UserBean" %>
<%@ page import="java.util.List" %>
<%@ page import="fun.Client" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<table id="table" border="1">
<tr>
<th >id</th>
<th >name</th>
</tr>
<%
//的到数据库信息，放在list中
Client client=new Client();
List<UserBean> list= client.list();
if(list != null){
for(UserBean user : list){
%>
<tr >
<td ><%=user.getId()%></td>
<td ><%=user.getName()%></td>
</tr>
<%
}
}
%>
</table>
<div id="message"></div>
<script>
var websocket = null;
//判断当前浏览器是否支持WebSocket
if ('WebSocket' in window) {
//建立连接，这里的/websocket ，是ManagerServlet中开头注解中的那个值
websocket = new WebSocket("ws://localhost:8080/websocket");
}
else {
alert('当前浏览器 Not support websocket')
}
//连接发生错误的回调方法
websocket.onerror = function () {
setMessageInnerHTML("WebSocket连接发生错误");
};
//连接成功建立的回调方法
websocket.onopen = function () {
setMessageInnerHTML("WebSocket连接成功");
}
//接收到消息的回调方法
websocket.onmessage = function (event) {
setMessageInnerHTML(event.data);
if(event.data=="1"){
location.reload();
}
}
//连接关闭的回调方法
websocket.onclose = function () {
setMessageInnerHTML("WebSocket连接关闭");
}
//监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。
window.onbeforeunload = function () {
closeWebSocket();
}
//将消息显示在网页上
function setMessageInnerHTML(innerHTML) {
document.getElementById('message').innerHTML += innerHTML + '<br/>';
}
//关闭WebSocket连接
function closeWebSocket() {
websocket.close();
}
</script>
</body>
</html>
前面插入的java代码得到数据库中的信息，后面的js代码实现websocket通讯。
ManagerServlet.java:
package fun;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.sql.PreparedStatement;
import java.util.concurrent.CopyOnWriteArraySet;
/**
* 这个类即实现了进行数据库操作的Servlet类，又实现了Websocket的功能.
*/
//该注解用来指定一个URI，客户端可以通过这个URI来连接到WebSocket，类似Servlet的注解mapping；
// servlet的注册放在了web.xml中。
@ServerEndpoint(value = "/websocket")
public class ManagerServlet extends HttpServlet {
//concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象。若要实现服务端与单一客户端通信的话，可以使用Map来存放，其中Key可以为用户标识
private static CopyOnWriteArraySet<ManagerServlet> webSocketSet = new CopyOnWriteArraySet<ManagerServlet>();
//这个session不是Httpsession，相当于用户的唯一标识，用它进行与指定用户通讯
private javax.websocket.Session session=null;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException {
String msg;
String name=request.getParameter("name");
//这里submit是数据库操作的方法，如果插入数据成功，则发送更新信号
if(submit(name)){
//发送更新信号
sendMessage();
msg="ok!";
}else {
msg="error!";
}
response.sendRedirect("manager.jsp?msg="+msg);
}
public void doPost(HttpServletRequest request,HttpServletResponse reponse) throws ServletException, IOException {
doGet(request,reponse);
}
/**
* 向数据库插入一个name
* @param name
* @return
*/
public boolean submit(String name){
DB db=new DB();
String sql="insert into users(name) values(?)";
try{
PreparedStatement pstmt=db.con.prepareStatement(sql);
pstmt.setString(1,name);
pstmt.executeUpdate();
return true;
}catch (Exception e){
e.printStackTrace();
return false;
}finally {
db.close();
}
}
/**
* @OnOpen allows us to intercept the creation of a new session.
* The session class allows us to send data to the user.
* In the method onOpen, we'll let the user know that the handshake was
* successful.
* 建立websocket连接时调用
*/
@OnOpen
public void onOpen(Session session){
System.out.println("Session " + session.getId() + " has opened a connection");
try {
this.session=session;
webSocketSet.add(this); //加入set中
session.getBasicRemote().sendText("Connection Established");
} catch (IOException ex) {
ex.printStackTrace();
}
}
/**
* When a user sends a message to the server, this method will intercept the message
* and allow us to react to it. For now the message is read as a String.
* 接收到客户端消息时使用，这个例子里没用
*/
@OnMessage
public void onMessage(String message, Session session){
System.out.println("Message from " + session.getId() + ": " + message);
}
/**
* The user closes the connection.
*
* Note: you can't send messages to the client from this method
* 关闭连接时调用
*/
@OnClose
public void onClose(Session session){
webSocketSet.remove(this); //从set中删除
System.out.println("Session " +session.getId()+" has closed!");
}
/**
* 注意: OnError() 只能出现一次. 其中的参数都是可选的。
* @param session
* @param t
*/
@OnError
public void onError(Session session, Throwable t) {
t.printStackTrace();
}
/**
* 这个方法与上面几个方法不一样。没有用注解，是根据自己需要添加的方法。
* @throws IOException
* 发送自定义信号，“1”表示告诉前台，数据库发生改变了，需要刷新
*/
public void sendMessage() throws IOException{
//群发消息
for(ManagerServlet item: webSocketSet){
try {
item.session.getBasicRemote().sendText("1");
} catch (IOException e) {
e.printStackTrace();
continue;
}
}
}
}
建议到flask官网学习一下。
一楼和二楼是同一个答案，建议直接去查看二楼的原始链接