What's the proper way of terminating a Node.js server request?

I'm playing around with a basic Node.js server (no frameworks). I want the server to terminate the request under certain conditions. What's the proper way of doing this? I tried request.connection.destroy(), req.removeListener('data'), and req.removeListener('end'), but the server keeps going and returns results. Here's part of what I have:

http.createServer(function(req,res){
    req.on('data',function(data){
        content+=data;
        if(condition){
            req.connection.destroy();
            req.removeListener('data');
            req.removeListener('end');
        }
    });

    req.on('end',function(){=
        res.writeHead(200,{
            'Context-Type':'text/plain',
        });
        res.write(content);
        res.end();
    });
});

P.S. Isn't it better to do req.once('end',...) instead of req.on('end',...)? Everyone one else seems to use on(), is there a reason for that?