How can I wait for socket events in Javascript?-CodePudding

I am trying to use datagram sockets to make a simple game in Javascript, but I can't figure out how to wait for events like bind or message to happen. Can I use promisify for that?

This is my current code:

import { createSocket } from 'dgram';
import * as readline from 'node:readline/promises';
import { stdin as input, stdout as output } from 'node:process';

const client = createSocket('udp4');

const rl = readline.createInterface({ input, output });

client.on('connect', () => { console.log(`connected: ${client.remoteAddress().address}:${client.remoteAddress().port}`); });
client.on('close', () => { console.log('closed'); });

client.on('listening', () => {
    const addr = client.address();
    console.log(`client listening on ${addr.address}:${addr.port}`);
});

client.bind();

const address = await rl.question('Enter address: ');

And the terminal output:

➜ node client.mjs
Enter address: client listening on 0.0.0.0:50432

Is question() being called before bind() is done or is it the event that is being triggered after question()? Either way, how can I ask for the address that I am going to message after bind() is done and the client address in shown?

CodePudding user response：

You can wrap the asynchronous UDP initialization in a function that returns a promise so the caller can know when it's done:

function initUDP() {

    return new Promise((resolve, reject) => {
        const client = createSocket('udp4');

        client.on('connect', () => { console.log(`connected: ${client.remoteAddress().address}:${client.remoteAddress().port}`); });
        client.on('close', () => { console.log('closed'); });

        client.on('listening', () => {
            const addr = client.address();
            console.log(`client listening on ${addr.address}:${addr.port}`);
            resolve(client);
        });

        client.bind();
        client.on('error', reject);
    });
}

initUDP().then(async client => {
    const rl = readline.createInterface({ input, output });
    const address = await rl.question('Enter address: ');

}).catch(err => {
    console.log(err);
});

Note: The listening event does the same thing as the callback you can pass to .bind() so you just need to do one or the other.

CodePudding user response：

Enter port when binding. nodejs-dgram