node.js giving Error: bind EINVAL

node.js giving Error: bind EINVAL

I am learning Node.js and i am doing some sample code on udp .I am trying
to implement a udp server to listen to multicast message and my basic code
is this
var server = require('dgram').createSocket('udp4');
server.on('message', function(message, rinfo) {
console.log('server got message: ' + message + ' from ' + rinfo.address +
':' + rinfo.port);
});
server.bind(4000);
server.addMembership('230.1.2.3');
but node gives me an error,
events.js:72
throw er; // Unhandled 'error' event
Error: bind EINVAL
at errnoException (dgram.js:440:11)
at dgram.js:207:28
at dns.js:72:18
at process._tickCallback (node.js:415:13)
at Function.Module.runMain (module.js:499:11)
at startup (node.js:119:16)
at node.js:901:3
also i am using windows 7 .please help...