在 Express.js 路由中发送 websocket 消息

Question

目标：

假设我们有一个充满商店的市场。 我正在为店主创建一个特定页面localhost:3000/livePurchases/:storeId来监控他们何时获得新购买的实时通知。

alert('you received a new purchase')应在购买商品时由 WebSocket 触发。

问题：

我需要在我的 express 服务器上设置 WebSocket，以便可以在我的代码中与设置 websocket 服务器的位置不同的地方触发 websocket。 但我不明白如何做到这一点。

在成功购买商品后，客户的浏览器将请求路由/newPurchase/:storeId 。 websocket 应在"/newPurchase/:storeId" （后端）的路由代码内向"/livePurchases/:storeId" （前端）上的 websocket 发送一条消息，店主可以在其中监控实时购买。

app.js

const express = require("express");

module.exports = (config) => {
  const app = express();

  app.post("/newPurchase/:storeId", (req, res, next) => {
    const { storeId } = req.params;
    // trigger websocket message to `localhost:3000/livePurchases/:storeId`
    // when client requests this route

  });

  return app;
};

但是 app.js 是从另一个脚本www.js导出和运行的。 在实际场景中，这是在运行应用程序之前连接数据库：

www.js

const app = require("../server/app")();

const port = process.env.PORT || "4000";
app.set("port", port);

app
  .listen(port)
  .on("listening", () =>
    console.log("info", `HTTP server listening on port ${port}`)
  );

module.exports = app;

这意味着需要在www.js中设置 web 套接字服务器。

下面是我从本教程中获得的通知服务，它似乎试图解决我遇到的问题，但没有解释如何实现它。 它是一个处理 websocket 的 class。

NotifierService.js

const url = require("url");
const { Server } = require("ws");

class NotifierService {
  constructor() {
    this.connections = new Map();
  }

  connect(server) {
    this.server = new Server({ noServer: true });
    this.interval = setInterval(this.checkAll.bind(this), 10000);
    this.server.on("close", this.close.bind(this));
    this.server.on("connection", this.add.bind(this));
    server.on("upgrade", (request, socket, head) => {
      console.log("ws upgrade");
      const id = url.parse(request.url, true).query.storeId;

      if (id) {
        this.server.handleUpgrade(request, socket, head, (ws) =>
          this.server.emit("connection", id, ws)
        );
      } else {
        socket.destroy();
      }
    });
  }

  add(id, socket) {
    console.log("ws add");
    socket.isAlive = true;
    socket.on("pong", () => (socket.isAlive = true));
    socket.on("close", this.remove.bind(this, id));
    this.connections.set(id, socket);
  }

  send(id, message) {
    console.log("ws sending message");

    const connection = this.connections.get(id);

    connection.send(JSON.stringify(message));
  }

  broadcast(message) {
    console.log("ws broadcast");
    this.connections.forEach((connection) =>
      connection.send(JSON.stringify(message))
    );
  }

  isAlive(id) {
    return !!this.connections.get(id);
  }

  checkAll() {
    this.connections.forEach((connection) => {
      if (!connection.isAlive) {
        return connection.terminate();
      }

      connection.isAlive = false;
      connection.ping("");
    });
  }

  remove(id) {
    this.connections.delete(id);
  }

  close() {
    clearInterval(this.interval);
  }
}

module.exports = NotifierService;

我停止实施“NotifierService”的地方

我在 www.js 中添加了带有NotifierService的www.js服务器

www.js with websockets added

const app = require("../server/app")();
const NotifierService = require("../server/NotifierService.js");
const notifier = new NotifierService();
const http = require("http");
const server = http.createServer(app);
notifier.connect(server);
const port = process.env.PORT || "4000";
app.set("port", port);

server
  .listen(port)
  .on("listening", () =>
    console.log("info", `HTTP server listening on port ${port}`)
  );

module.exports = app;

但是现在如何从后端app.js中的/newPurchase路由发送 websocket 消息？ 如果我在app.js中创建一个新的NotifierService实例，以便在/newPurchase路由中使用notifierService.send方法，那么新的NotifierService实例将无法访问 websocket 连接，因为它与一项在www.js上发起。

前端：

App.js

import React from "react";

import { BrowserRouter as Router, Switch, Route } from "react-router-dom";
import LiveStorePurchases from "./LiveStorePurchases";

function App(props) {
  return (
    <div className="App">
      <Router>
        <Switch>
          <Route exact path="/livePurchases/:storeId">
            <LiveStorePurchases />
          </Route>
        </Switch>
      </Router>
    </div>
  );
}

export default App;

LivePurchaseServer.js

import React, { useEffect, useState } from "react";
import { useParams } from "react-router-dom";

export default function LiveStorePurchases() {
  let { storeId } = useParams();
  const URL = "ws://127.0.0.1:4000?storeId=" + storeId;

  const [ws, setWs] = useState(new WebSocket(URL));

  useEffect(() => {
    ws.onopen = (e) => {
      newFunction(e);

      function newFunction(e) {
        alert("WebSocket Connected");
      }
    };

    ws.onmessage = (e) => {
      const message = e.data;
      alert(message);
    };

    return () => {
      ws.onclose = () => {
        alert("WebSocket Disconnected");
        setWs(new WebSocket(URL));
      };
    };
  }, [ws.onmessage, ws.onopen, ws.onclose, ws, URL]);

  return (
    <div
      style={{
        color: "red",
        fontSize: "4rem",
      }}
    >
      store: {storeId}
    </div>
  );
}

Answer 1

app.js ：

我能够将 websocket 实例移动到app.js而不是www.js 。 然后我只是将该实例传递给其他路线。

const express = require("express");
const NotifierService = require("../server/NotifierService.js");
const notifier = new NotifierService();
const http = require("http");
const routes = require("./routes");

module.exports = (config) => {
  const app = express();
  const server = http.createServer(app); // websocket created
  notifier.connect(server);              // and connected here in app.js

  //   I moved POST /newPurchase to routes.js in order
  //   to demonstrate how the notifier instance can be
  //   passed around to different routes
  app.use(routes(notifier));

  return server;
};

routes.js ：

我创建了一个路由文件routes.js以表明您可以移动通知程序实例并从任何路由调用它。

const express = require("express");

const router = express.Router();

// I moved "/newPurchase/:id" to this routes.js file to show that
// I could move the notifier instance around.

module.exports = (webSocketNotifier) => {
  router.post("/newPurchase/:id", (req, res, next) => {
    webSocketNotifier.send(req.params.id, "purchase made");
    res.status(200).send();
  });
  return router;
};

www.js ：

const server = require("../server/app")();

const port = process.env.PORT || "4000";

server
  .listen(port)
  .on("listening", () =>
    console.log("info", `HTTP server listening on port ${port}`)
  );

module.exports = server;