title: sending a socket.io .once message
body: <p>This would work without the .once call.</p>
  
  <p>I am trying to send a single message from server side code with</p>
  
  <p><code>io.on('connect', function (socket) {
  socket.once('connect', function() {
  socket.emit('mydata', { feed: result});</code></p>
  
  <p>but I get nothing on the client side unless I remove the second line.
  I also tried socket.once('mydata', { feed: result}) but:</p>
  
  <pre><code>throw new TypeError('listener must be a function');
  </code></pre>
  
  <p>In other words how can one send a message to the client side only when there is new 'mydata'? </p>
  
  <p>Thanks</p>