作者: Claire Chang

I have found:

• “ping timeout”: client stopped responding to pings in the allotted amount of time (per the pingTimeout config setting).
• “transport close”: this appears to happen if the client side stopped sending data at all… or maybe there’s some kind of callback causing this to happen. I can see it happen if I just close a tab or follow a link from a page where I have an active connection to the server. But I’m not clear if this is always a case of the client causing it to happen.

  Sorry for re-opening the issue. Regarding the transport close that is the reason when page is closed/reloaded, it also happens some times in bad network conditions specifically when the ping packets are not delivered to the client. For the latter I need to handle it in the server side by waiting for the client to reconnect. Is there a way to properly distinguish between these two?

• “Client namespace disconnect”: When the client sends a disconnect packet (client.disconnect())
• “server namespace disconnect”: Looks to be when the server performs a socket.disconnect() action.
• “Transport error”: An error occurred, I assume this is a server side error, but I’m not totally clear, as I’ve not been able to trigger one on my own.
• “io server disconnect” This occurs using a third party library socketIOAuth when authentication fails

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Socket.io

socket.io是基於Websocket的Client-Server實時通信庫

Socket.io承繼了Node.js的事件處理方法，把Client端與Server端的程式統一成一至的操作方式，讓使用者可以只需專注在處理「事件」，就可以快速開發出應用，他也支援『房間』的概念，可以使用同一條WebSocket卻擁有不被彼此干擾的資料傳輸（多種聊天頻道的概念）。另外，他也提供了很好的fallback機制，即使用戶的瀏覽器不支援WebSocket，他還是可以利用Flash、XMLHttpRequest等方式來傳送資訊（速度會比較慢就是了）。這些機制都他都包裝好了，所以寫程式時並不需要知道這些細節，只需要設定好就可以運作。

Socket.io 特性整理

• Events 自訂事件。
• Rooms Room 的概念只存在於伺服器端。可以理解為訊息處理時的聽眾分組，可對同一個分組內的聽眾進行廣播。
• Namespaces 命名空間，我理解為底層連線的分組管理，不同命名空間可以走同一條 Engine.io 連線或是各自連線，每個命名空間可以各自驗證是否接受連線。
• ACK 回調 如同 HTTP 之於 TCP，HTTP 為 TCP 提供了一套請求與響應的模型。ACK 也為 Socket.io 提供了一套請求與響應的通訊模型。
• 連線維護
• 自動斷線重連
• ping/pong 心跳

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伺服器端

範例程式碼:

import express from "express";
import http from "http";

const app = express();
const server = http.createServer(app);

const sio = require("socket.io")(server, {
    handlePreflightRequest: (req, res) => {
        const headers = {
            "Access-Control-Allow-Headers": "Content-Type, Authorization",
            "Access-Control-Allow-Origin": req.headers.origin, //or the specific origin you want to give access to,
            "Access-Control-Allow-Credentials": true
        };
        res.writeHead(200, headers);
        res.end();
    }
});

sio.on("connection", () => {
    console.log("Connected!");
});

server.listen(3000);

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參考文章

Socket.io 1.x: use WebSockets only?

相關參數

這個問題主要可參考Engine.io介紹的連線設定的章節
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