debug_test.js

function mutualSubscribe(source, friend, callback) {
    var XMPP = require('stanza.io');
    var friend_jid = friend.toLowerCase() + '@xxxx.me';
    var source_jid = source.toLowerCase() + '@xxxx.me';

    var source_client = XMPP.createClient({
        jid: source_jid,
        password: 'xyz',
        transport: 'bosh',
        boshURL: config.get('xmpp.bosh_url')
    });

    var friend_client = XMPP.createClient({
        jid: friend_jid,
        password: 'xyz',
        transport: 'bosh',
        boshURL: config.get('xmpp.bosh_url')
    });

    function notAlreadySubscribed(jid, client, callback) {
        var sendSubscribe = true;
        client.getRoster(function (error, roster) {
            if (error) throw error;
            var contact = (roster.roster) ? _.find(roster.roster.items, function (r) {
                return r.jid.bare == jid; //  pres.from.local
            }) : null;
            console.log('roster','looking up '+jid +' for '+client.jid.bare,contact);
            if (contact) {
                sendSubscribe = (contact.subscription !== 'both' || (contact.subscription !== 'to')) && !contact.subscriptionRequested; //|| contact.subscription !== 'from'
            }
        });
        callback(null, sendSubscribe);
    }

    source_client.on('subscribe', function (pres) {
        source_client.acceptSubscription(pres.from.bare); // accept the subscription we received
        console.log('4. ' + source + ' accepts subscription from ' + pres.from.bare);
    });

    friend_client.on('subscribe', function (pres) {
        friend_client.acceptSubscription(pres.from.bare); // accept the subscription we received
        console.log('2. ' + friend + ' accepts subscription from ' + pres.from.bare);
        notAlreadySubscribed(pres.from.bare, friend_client, function (err, sendSubscribe) {
            if (sendSubscribe) {
                console.log('3. ' + friend + ' sends subscribe to ' + pres.from.bare);
                friend_client.subscribe(pres.from.bare); // send a subscribe the other way
            }

        });

    });


    source_client.on('session:started', function () {
        console.log('xmpp session started for ' + source_jid);
        source_client.sendPresence();
        console.log('1.' + source + ' sends subscribe to ' + friend_jid);
        source_client.subscribe(friend_jid);

    });

    friend_client.on('session:started', function () {
        console.log('xmpp session started for ' + friend_jid);
        friend_client.sendPresence();
    });

    source_client.on('subscribed', function (pres) {
        console.log('!!!', '6. ' + source + ' is now subscribed to ' + pres.from.bare);
    });

    friend_client.on('subscribed', function (pres) {
        console.log('!!!', '5. ' + friend + ' is now subscribed to ' +  pres.from.bare);
       // source_client.sendPresence();
       // source_client.disconnect();
       // friend_client.disconnect();

        //  clearTimeout(friend_session_timeout);
    });

    friend_client.on('session:end', function () {
        console.log(friend_jid, 'xmpp session ended');
        // -- check if we really succeeded
        callback(null, null);
    });

    source_client.on('session:end', function () {
        console.log(source_jid, 'xmpp session ended');
        //friend_client.disconnect();
    });

    source_client.connect();
    friend_client.connect();
}


mutualSubscribe('userA', 'userB', function (error, result) {
    console.log('subscription processed');
});