13-1 WebSocket是什么
WebSocket简介:
WebSocket是一种在单个TCP连接上进行全双工通信的协议。 WebSocket使得客户端和服务器之间的数据交换变得更加简单,允许服务端主动向客户端推送数据。 在WebSocket API中,浏览器和服务器只需要完成一次握手,两者之间就直接可以创建持久性的连接,并进行双向数据传输。
WebSocket和HTTP的相同点和不同点:
WebSocket和HTTP都是解决 客户端-服务端 通信的网络协议。 HTTP是单向的,客户端先发起请求,服务端收到请求后再处理这个请求返回响应结果;即先有请求再有响应,且是一个请求对应一个响应;请求时建立连接,响应后断开连接。 WebSocket是双向的,客户端发起请求经过三次握手连接后,客户端和服务端就会基于这个连接保持通信,都可以主动向对方发消息。任何一端都可以主动断开这个连接。 HTTP是无状态的,WebSocket是有状态的。即如果使用WebSocket,那么只要建立了连接,每次通信时,服务端都知道在和谁通信,不需要借助Cookie或seesion或jwt等登录认证方式。
参考:https://www.geeksforgeeks.org/what-is-web-socket-and-how-it-is-different-from-the-http/
WebSocket的应用:
实时web应用游戏聊天软件等等
13-2 WebSocket聊天室简易版
使用FastAPI演示浏览器和服务端基于WebSocket,建立连接并双向通信。 前端代码无需掌握,只要了解它在干什么事情即可。 示例中,我们使用 HTMLResponse,通过接口的方式把前端代码响应的浏览器上;但其实直接写一个html文件,手动打开也可以的。 后端使用WebSocket,需要使用WebSocket这个对象,常用如下三个 协程函数。
await websocket.accept() # 建立连接
data = await websocket.receive_text() # 收消息
await websocket.send_text() # 发消息
想要在fastAPI中使用websocket 需要安装标准版的uvicorn
pip3 install uvicorn[standard]
实例:简单版聊天
from fastapi import FastAPI, WebSocket
from fastapi.responses import HTMLResponse
app = FastAPI()
html = """
WebSocket Chat
var ws = new WebSocket("ws://localhost:8000/ws");
ws.onmessage = function(event) {
var messages = document.getElementById('messages')
var message = document.createElement('li')
var content = document.createTextNode(event.data)
message.appendChild(content)
messages.appendChild(message)
};
function sendMessage(event) {
var input = document.getElementById("messageText")
ws.send(input.value)
input.value = ''
event.preventDefault()
}
"""
@app.get("/")
async def get():
return HTMLResponse(html)
@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
await websocket.accept()
while True:
data = await websocket.receive_text()
await websocket.send_text(f"Message text was: {data}")
13-3 WebSocket多人在线聊天室
实现多人在线聊天室处理客户端下线通知使用时间戳做客户端id
示例1:多人在线聊天室
from typing import List
from fastapi import FastAPI, WebSocket, WebSocketDisconnect
from fastapi.responses import HTMLResponse
app = FastAPI()
html = """
WebSocket Chat
Your ID:
var client_id = Date.now()
document.querySelector("#ws-id").textContent = client_id;
var ws = new WebSocket(`ws://localhost:8000/ws/${client_id}`);
ws.onmessage = function(event) {
var messages = document.getElementById('messages')
var message = document.createElement('li')
var content = document.createTextNode(event.data)
message.appendChild(content)
messages.appendChild(message)
};
function sendMessage(event) {
var input = document.getElementById("messageText")
ws.send(input.value)
input.value = ''
event.preventDefault()
}
"""
class ConnectionManager:
def __init__(self):
self.active_connections: List[WebSocket] = []
async def connect(self, websocket: WebSocket):
await websocket.accept()
self.active_connections.append(websocket)
def disconnect(self, websocket: WebSocket):
self.active_connections.remove(websocket)
async def send_personal_message(self, message: str, websocket: WebSocket):
await websocket.send_text(message)
async def broadcast(self, message: str):
for connection in self.active_connections:
await connection.send_text(message)
manager = ConnectionManager()
@app.get("/")
async def get():
return HTMLResponse(html)
@app.websocket("/ws/{client_id}")
async def websocket_endpoint(websocket: WebSocket, client_id: int):
await manager.connect(websocket) # 接收连接
try:
while True:
data = await websocket.receive_text() # 接收数据
await manager.send_personal_message(f"You wrote: {data}", websocket) # 自己发的消息自己看到
await manager.broadcast(f"Client #{client_id} says: {data}") # 广播,发给所有在线的客户端
except WebSocketDisconnect:
manager.disconnect(websocket) # 断开连接
await manager.broadcast(f"Client #{client_id} left the chat") # 广播
示例2:优化自己发的消息不重复展示
from typing import List
from fastapi import FastAPI, WebSocket, WebSocketDisconnect
from fastapi.responses import HTMLResponse
app = FastAPI()
html = """
WebSocket Chat
Your ID:
var client_id = Date.now()
document.querySelector("#ws-id").textContent = client_id;
var ws = new WebSocket(`ws://localhost:8000/ws/${client_id}`);
ws.onmessage = function(event) {
var messages = document.getElementById('messages')
var message = document.createElement('li')
var content = document.createTextNode(event.data)
message.appendChild(content)
messages.appendChild(message)
};
function sendMessage(event) {
var input = document.getElementById("messageText")
ws.send(input.value)
input.value = ''
event.preventDefault()
}
"""
class ConnectionManager:
def __init__(self):
self.active_connections: List[WebSocket] = []
async def connect(self, websocket: WebSocket):
await websocket.accept()
self.active_connections.append(websocket) # 收集有所的在线客户端
def disconnect(self, websocket: WebSocket):
self.active_connections.remove(websocket) # 当客户端断线时,更新在线客户端列表
async def send_personal_message(self, message: str, websocket: WebSocket):
await websocket.send_text(message)
async def broadcast(self, message: str, websocket: WebSocket):
for connection in self.active_connections:
if connection == websocket: # 判断下,如果是自己就不再发送消息
continue
await connection.send_text(message)
manager = ConnectionManager()
@app.get("/")
async def get():
return HTMLResponse(html)
@app.websocket("/ws/{client_id}")
async def websocket_endpoint(websocket: WebSocket, client_id: int):
await manager.connect(websocket)
try:
while True:
data = await websocket.receive_text()
await manager.send_personal_message(f"You wrote: {data}", websocket)
await manager.broadcast(f"Client #{client_id} says: {data}", websocket)
except WebSocketDisconnect:
manager.disconnect(websocket)
await manager.broadcast(f"Client #{client_id} left the chat", websocket)
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