It's hard for us to know with so little information. If you post your code, we are more likely to know what's going on.

Looking at the hello world demo on the nowjs.com site, it looks like maybe you don't have the helloworld_server.js file included in your page because that's where the distributeMessage() function is defined.

In the demo files here, helloworld.html has this line:

<script src="http://localhost:8080/nowjs/now.js"></script>

But, the demo tgz file doesn't include that. You are probably missing now.js in an appropriate path.