时间戳

首页 > 解决方案 > Python websockets，如何从函数发送消息

python - Python websockets，如何从函数发送消息

问题描述

我正在编写我的代码更新，以将 WebSocket 消息发送到连接的 Web 浏览器，它需要更新其数据（图表 Web 应用程序）。当代码将新数据插入 MySQL 数据库时，需要发送此消息。我将在浏览器中编写一些 Javascript，以便在收到消息时获取更新。

我的测试代码：

import asyncio
#import time
import websockets


def readValues():
    '''do stuff that returns the values for database'''
    pass


def inserdata(val):
    '''insert values into mysql'''
    pass


async def ph(websocket, path):
    while True:
        message = 'update' 
        # here we receive message that the data
        # has been added and need to message the
        # browser to update
        print('socket executed')
        await websocket.send(message)
        await asyncio.sleep(2)
        # shouldn't be needed as message
        # sent only when updated data
        # inserted(every 20s)


async def main():  # maybe use this to get/write to the database etc
    while True:  # instead of the loop at bottom
        print('main executed')
        await asyncio.sleep(20)

start_server = websockets.serve(ph, '0.0.0.0', 5678)

asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_until_complete(main())
asyncio.get_event_loop().run_forever()

#below copied from current program
'''
while 1:
    try:
        a = readValues() #read valves from a function
        insertdata(a) #function to write values to mysql

        #some method to send the message to the web browser via -
        #websocket, that it needs to get the new data

        time.sleep(20) #wait and then do it again
    except Exception as e:
        print(e)
'''

我可以使用消息变量发送消息。

无论 WebSocket 发生了什么，我都需要 readValues 和 insert data 函数每 20 秒连续运行一次。

但我不知道如何从更新数据库的功能向浏览器发送消息。而且我无法找出同时运行 WebSocket 进程和更新数据库的最佳方法。

我在代码中写了注释，试图帮助你理解我想要做什么。

希望各位大侠能理解，谢谢。

更新：感谢 Nathan：我更改了代码并执行了 2 个文件，如下所示：服务器：

import asyncio
import websockets

async def ph(websocket, path):
    while True:
        need_update = await websocket.recv()
        print('socket executed')
        await websocket.send(need_update)


start_server = websockets.serve(ph, '0.0.0.0', 5678)

asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()

处理文件：

import asyncio
import time
import websockets

async def main():
    async with websockets.connect('ws://127.0.0.1:5678') as websocket:
        while 1:
            try:
                #a = readValues() #read values from a function
                #insertdata(a) #function to write values to mysql
                await websocket.send("updated")
                print('data updated')
                time.sleep(20) #wait and then do it again
            except Exception as e:
                print(e)

asyncio.get_event_loop().run_until_complete(main())

然后我运行了这两个（完全如图所示）并用这个打开了一个网络浏览器：

<!DOCTYPE html>
<html>
    <head>
    </head>
    <body>
        <h3>
        Test
        </h3>
        <p>
            <div id="log"></div>
        </p>
        <script>
            // helper function: log message to screen
            function log(msg) {
                document.getElementById('log').innerText += msg + '\n';
            }

            // setup websocket with callbacks
            var ws = new WebSocket('ws://192.168.0.224:5678/');
            ws.onopen = function() {
                log('CONNECT');
            };
            ws.onclose = function() {
                log('DISCONNECT');
            };
            ws.onmessage = function(event) {
                log('MESSAGE: ' + event.data);
            };
        </script>
    </body>
</html>

在我按上述方式打开浏览器之前，一切似乎都很好。然后除了“连接”结果之外，浏览器什么也没有。

WebSocket连接关闭：code = 1006（连接异常关闭[内部]），无原因

出现在两个脚本上。

标签： pythonwebsocket

解决方案

您需要“数据库处理程序”和套接字服务器之间的套接字连接：

使用主循环创建第二个脚本：

 async def main():
    async with websockets.connect(websocket_address) as websocket:
        while 1:
            try:
                a = readValues() #read values from a function
                insertdata(a) #function to write values to mysql
                await websocket.send("some token to recognize that it's the db socket")
                time.sleep(20) #wait and then do it again
             except Exception as e:
                print(e)

asyncio.get_event_loop().run_until_complete(main())

然后在另一个脚本上你可以：

    USERS = set()
    def register(websocket):
        USERS.add(websocket)

    async def ph(websocket, path):
        while True:
            register(websocket) #not sure if you need to place it here
            need_update = await websocket.recv()
            #check unique token to verify that it's the database
            message = 'update'#here we receive message that the data
                              #has been added and need to message the
                              #browser to update
            print('socket executed')
            if USERS:       # asyncio.wait doesn't accept an empty list
                await asyncio.wait([user.send(message) for user in USERS])


    start_server = websockets.serve(ph, '0.0.0.0', 5678)

    asyncio.get_event_loop().run_until_complete(start_server)
    asyncio.get_event_loop().run_forever()

推荐阅读