Yes, it is no longer synchronous. You can check the docs too.
Important note: the behavior of dgram.Socket#bind() has changed in v0.10 and is always asynchronous now.
If you have code that looks like this:
var s = dgram.createSocket('udp4');
s.bind(1234);
s.addMembership('224.0.0.114');
You have to change it to this:
var s = dgram.createSocket('udp4');
s.bind(1234, function() {
s.addMembership('224.0.0.114');
});
It will be like this so you would have to change your code.