How to listen to an event after emitting an event Socket.io
Question
I want to build an SQL handler server side on my nodejs server.
I would like my nodejs to recieve requests from client side - for example:
client.js
socket.emit("sql-query", "SELECT * FROM *");
socket.on('sql-response', results => {
do things with results...
}
server.js
socket.on('sql-query', query => {
connection.query(query, function(error, results, fields)) {
if(results > 0) socket.emit('sql-response', results);
else console.log('No results... yet !');
}
});
Problem is, if I do that, every function that needs to make an SQL request will get the sql-response event.
I would want my emit to return results without having to catch another event (that every file using SQL request will catch).
Something like this: server.js
socket.on('sql-query', query => {
connection.query(query, function(error, results, fields)) {
if(results > 0) socket.return(results); //I know this is wrong and that's not how events work.
}
});
General idea: Make SQL requests using a nodejs / socket.io server from other files.
Please tell me if it's a headache to do that and if there is another better way of achieving this.
Thank you
1 answers
solution1
0 2021-04-15 20:03:28
I am not pretty sure If I got you, but for me, it works as you want, but it is the same code that you are using, because socket.emit does not multicast
Server
const express = require('express');
const app = express();
const http = require('http');
const server = http.createServer(app);
const io = require('socket.io')(server);
app.get('/', (req, res) => {
res.sendFile(__dirname + '/index.html');
});
io.on('connection', (socket) => {
socket.on('sql-query', (query) => {
socket.emit('sql-response', `this is your response: ${query}`);
});
});
server.listen(3000, () => {
console.log('listening on *:3000');
});
Client
<!DOCTYPE html>
<html>
<head>
<title>Socket.IO chat</title>
<style>
body { margin: 0; padding-bottom: 3rem; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; }
#form { background: rgba(0, 0, 0, 0.15); padding: 0.25rem; position: fixed; bottom: 0; left: 0; right: 0; display: flex; height: 3rem; box-sizing: border-box; backdrop-filter: blur(10px); }
#input { border: none; padding: 0 1rem; flex-grow: 1; border-radius: 2rem; margin: 0.25rem; }
#input:focus { outline: none; }
#form > button { background: #333; border: none; padding: 0 1rem; margin: 0.25rem; border-radius: 3px; outline: none; color: #fff; }
#messages { list-style-type: none; margin: 0; padding: 0; }
#messages > li { padding: 0.5rem 1rem; }
#messages > li:nth-child(odd) { background: #efefef; }
</style>
<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/4.0.1/socket.io.js" integrity="sha512-q/dWJ3kcmjBLU4Qc47E4A9kTB4m3wuTY7vkFJDTZKjTs8jhyGQnaUrxa0Ytd0ssMZhbNua9hE+E7Qv1j+DyZwA==" crossorigin="anonymous"></script>
</head>
<body>
<ul id="messages"></ul>
<form id="form" action="">
<input id="input" autocomplete="off" /><button>Send</button>
</form>
</body>
<script>
var socket = io();
var form = document.getElementById('form');
var input = document.getElementById('input');
form.addEventListener('submit', function(e) {
e.preventDefault();
if (input.value) {
console.log(input.value)
socket.emit('sql-query', input.value);
input.value = '';
}
});
socket.on('sql-response', function(msg) {
var item = document.createElement('li');
item.textContent = msg;
messages.appendChild(item);
window.scrollTo(0, document.body.scrollHeight);
});
</script>
</html>
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