Socket.io 仅发出大写事件

Question

so I wanted to try out the socket.io library and all the examples work perfectly fine (with lowercase emits). But when I try to code my one little ping->pong it doesnt emit the events (I can view the message log in firefox network tab).

Code Server (Node JS):

const express = require("express");
const app = express();
const http = require("http").createServer(app);
const io = require("socket.io")(http);
const port = process.env.PORT || 9000;

app.use(express.static(__dirname + "/public"));

io.on("connection", (socket) => {
    console.log("Socket connected");
    socket.on("ping", () => {
        console.log("PING");
        socket.emit("pong", {});
    });
});

http.listen(port, () => console.log("listening on port " + port));

Code in Browser:

var socket = io();

socket.on("pong", () => {
    console.log("recieved PONG");
});

const ping = () => {
    socket.emit("ping");
};


document.addEventListener("mousedown", ping, false);

Strangely, this doesn't seem to work, "Socket connected" is printed, but the sockets don't emit anything. If I change the emits and on's from "ping"->"PING" and from "pong"->"PONG" everything works perfectly fine. Im just totally confused to why this is and why the examples can use lowercase emits.

Answer 1

Since there is nothing related with UPPERCASE/LOWERCASE event names, you may use them as you wish.

But ping/pong actually uses by socket.io server with several of them. you can see the list here . It's on bottom of the page =)

So unless you respest these you can use upper/lower case event/room names.

Also those event's are listenable by user too.

io.on('connect', onConnect);
function onConnect(socket) {
    socket.on('error', onError);
    socket.on('disconnect', onDisconnect);
    // ... and others too.

    // You can see and console on ping/pong events too.
    socket.on('ping', console.log);
    socket.on('pong', console.log);
}

I know socke.io's documentation really is not the best:D

By the way, ping and pong usage is coming from ws which also used by socket.io internally. If you want to see more about i'll leave links here where you can see ping and pong events emitting.

Sender.js: ping also Receiver.js: ping & pong