True Peer To Peer Connection Chat APP Using Node.JS.

nodep2p2.js

const dgram = require('dgram');
const readline = require('readline');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});

function ask(question) {
    return new Promise(resolve => rl.question(question, resolve));
}

async function findMyIP() {
    let req = await fetch("https://api64.ipify.org?format=json");
    req = await req.json();
    return req.ip;
}

findMyIP();
(async () => {
    // first find you ip 
    let myIP = await findMyIP();
    console.log("Your IP:", myIP);

    const myPort = parseInt(await ask("Your port (e.g. 12345): "));
    const peerIP = (await ask("Peer's PUBLIC IP: ")).trim();
    const peerPort = parseInt(await ask("Peer's port: "));

    // start udp server 
    const socket = dgram.createSocket('udp4');
    let connectionEstablished = false;

    // === Receive handler ===
    socket.on('message', (msg, rinfo) => {
        const data = msg.toString();

        if (data === 'punch') {
            socket.send('punch_ack', rinfo.port, rinfo.address);
        } else if (data === 'punch_ack') {
            if (!connectionEstablished) {
                console.log(`\n✅ Hole punch successful with ${rinfo.address}:${rinfo.port}`);
                connectionEstablished = true;
            }
        } else if (data === 'KEEP_ALIVE') {
            // ignore
        } else {
            console.log(`\n[From ${rinfo.address}:${rinfo.port}]: ${data}`);
            rl.prompt(true);
        }
    });

    socket.on('listening', () => {
        const address = socket.address();
        console.log(`\n🔌 Listening on ${address.address}:${address.port}`);
    });

    socket.bind(myPort);

    // === Punch hole ===
    function punchLoop() {
        let count = 0;
        const interval = setInterval(() => {
            if (connectionEstablished || count >= 20) {
                clearInterval(interval);
                if (!connectionEstablished) {
                    console.log("⚠️ Hole punching finished, but no ACK received.");
                    socket.close();
                    process.exit()
                }
                return;
            }

            socket.send('punch', peerPort, peerIP);
            count += 1;
        }, 500);
    }

    // === Keep alive ===
    function keepAlive() {
        setInterval(() => {
            socket.send('KEEP_ALIVE', peerPort, peerIP);
        }, 15000);
    }

    // === Chat loop ===
    function chatLoop() {
        console.log("💬 You can now chat! Type messages below:");
        rl.on('line', line => {
            socket.send(Buffer.from(line), peerPort, peerIP);
        });
    }

    // === Start everything ===
    punchLoop();
    keepAlive();

    const waitForConnection = setInterval(() => {
        if (connectionEstablished) {
            clearInterval(waitForConnection);
            chatLoop();
        }
    }, 1000);
})();