Django使用Channels实现WebSocket数据推送功能

Django使用Channels实现WebSocket消息通知功能

Channels 用于websocket通信，websocket是啥？主要实现在无客户端请求的情况下向客户端发送数据。

主要概念：频道，websocket是面向频道的，就好比微信群，一个微信群就是一个频道，你向频道发送内容，微信群内的所有人(连接到这个频道的客户端)都可以收到你的消息

本文主要写快速实现ws服务端

需要django3.0+，最好是在linux下进行测试开发，windows下安装时问题一大堆

安装：

pip install django>=3.0
pip install channels

创建project
```
django-admin startproject TestVideos
```
创建app
```
django-admin startapp chat
```

创建chat/routing.py

#django的路由叫urls.py
#对于channels有新的路由文件
from django.urls import re_path

from . import consumers  #等同于views.py 稍后创建

websocket_urlpatterns = [
    re_path(r'ws/chat/(?P<room_name>w+)/$', consumers.ChatConsumer.as_asgi()),
]

创建 chat/consumers.py

#等同于django的views.py
#对于channels叫consumers.py
#下面的内容作用：将新的ws客户端加入到一个频道，将其发送到ws服务端的内容广播至频道所有人
class ChatConsumer(AsyncWebsocketConsumer):
    async def connect(self):
        self.room_name = self.scope['url_route']['kwargs']['room_name']
        self.room_group_name = 'chat_%s' % self.room_name

        # Join room group
        await self.channel_layer.group_add(
            self.room_group_name,
            self.channel_name
        )

        await self.accept()

    async def disconnect(self, close_code):
        # Leave room group
        await self.channel_layer.group_discard(
            self.room_group_name,
            self.channel_name
        )

    # Receive message from WebSocket
    async def receive(self, text_data):
        message = dict(json.loads(text_data))

        # Send message to room group
        await self.channel_layer.group_send(
            self.room_group_name,
            {
                'type': 'chat_message',
                'message': message
            }
        )

    # Receive message from room group
    async def chat_message(self, event):
        message = event['message']

        # Send message to WebSocket
        await self.send(text_data=json.dumps({
            'message': message
        }))

修改settings.py

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    ...,
    'channels',   #ws服务端
    'chat',       #ws   app
]


#channels
ASGI_APPLICATION = "TestVideos.asgi.application"    #入口信息
CHANNEL_LAYERS = {    #频道后端，这里采用内存存储，默认是redis
    "default": {
        "BACKEND": "channels.layers.InMemoryChannelLayer"
    }
}

添加入口：

配置project/asgi.py(django3.0以前仅wsgi.py。和settings.py同级)

asgi.py原内容

"""
ASGI config for TestVideos project.

It exposes the ASGI callable as a module-level variable named ``application``.

For more information on this file, see
https://docs.djangoproject.com/en/3.1/howto/deployment/asgi/
"""

import os

from django.core.asgi import get_asgi_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'TestVideos.settings')

application = get_asgi_application()

asgi.py新内容

"""
ASGI config for main_project project.

It exposes the ASGI callable as a module-level variable named ``application``.

For more information on this file, see
https://docs.djangoproject.com/en/3.1/howto/deployment/asgi/
"""

import os

from django.core.asgi import get_asgi_application

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'BoatControlProject.settings')

# application = get_asgi_application()  #原本内容


from channels.routing import ProtocolTypeRouter, URLRouter  #channels
from channels.auth import AuthMiddlewareStack
import chat.routing    #我们创建的app


application = ProtocolTypeRouter({
    # "http": get_asgi_application(), #此处会影响http请求。此处大概时异步接管HTTP的意思

    "websocket": AuthMiddlewareStack(
        URLRouter(
            chat.routing.websocket_urlpatterns
        )
    ),
})

如何访问我们的ws，首先准备一个ws测试工具（用于向频道发送内容）。
```
使用这个：https://github.com/easy-swoole/wstool
```
在浏览器打开两个测试ws测试工具，都连接至同一个地址，client 1 发送数据， client 2 接收数据

其他的一些功能

当你有http请求或者其他地方需要向ws客户端发送内容时的写法：

from asgiref.sync import async_to_sync
from channels.layers import get_channel_layer

@method_decorator(csrf_exempt, name="dispatch")
class SendRoom(View):
    def dispatch(self, request, *args, **kwargs):

        return super(SendRoom, self).dispatch(request, *args, **kwargs)

    #测试频道广播
    def get(self, request, *args, **kwargs):
        event = {}
        event["message"] = {"latitudenum":37.553534,"longitudenum":122.083534,"yaw":90}

        channel_layer = get_channel_layer()     #重要代码
        async_to_sync(channel_layer.group_send)("chat_videos_stram", {"type": "chat_message","message": event["message"]})   #重要代码

        message = "ws send ok"
        return JsonResponse({"message": message})

    def post(self, request, *args, **kwargs):
        message = "post ok"

        return JsonResponse({"message": message})