How do I emit a message to all users in a private chat sharing a conversation\_id using node.js and socket.io?

```
var express = require('express'),
app = express(),
server = require('http').createServer(app),
io = require('socket.io').listen(server);
conversations = {};

app.get('/', function(req, res) {
res.sendfile('/');
});

io.sockets.on('connection', function (socket) {

socket.on('send message', function (data) {

    var conversation_id = data.conversation_id;

    if (conversation_id in conversations) {

        console.log (conversation_id + ' is already in the conversations object');

        // emit the message [data.message] to all connected users in the conversation

    } else {
        socket.conversation_id = data;
        conversations[socket.conversation_id] = socket;

        conversations[conversation_id] = data.conversation_id;

        console.log ('adding '  + conversation_id + ' to conversations.');

        // emit the message [data.message] to all connected users in the conversation

    }
})
});

server.listen(8080);

```