Web Sockets – Claire's Blog

Socket.io錯誤訊息意義

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

Socket.io介紹

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

Socket.io自行增加header

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);

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);

Error: probe transport websocket failed

參考文章

Socket.io 1.x: use WebSockets only?

Engine.io介紹

Socket.io是在engine.io的基礎上去實作的
Gitlab連結: Engine.IO: the realtime engine
engine.io為socket.io提供跨瀏覽器/跨設備的雙向通信的底層庫。engine.io使用了Websocket和XHR方式封裝了一套socket協議。在低版本的瀏覽器中，不支持Websocket，為了兼容使用長輪詢( polling )替代。

關於長輪詢可參考我的另一篇文章:WebSocket與Ajax的不同
過去WebSocket未出來時，許多聊天室使用的都是長輪詢的方式去實作，而engine.io則可依據客戶端環境兼容使用這兩種方式。
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Claire's Blog

分類: Web Sockets

Socket.io錯誤訊息意義

Socket.io介紹

Socket.io

Socket.io 特性整理

Socket.io自行增加header

伺服器端

Error: probe transport websocket failed

參考文章

相關參數

Engine.io介紹

Engine.io介紹