title: Channel.id () has been removed in netty4.0 final version, how can I solve?
body: <p>We update to netty4.0 final version, but Channel.id () has been removed.</p>
  
  <p>We need to take the initiative to send a message server to the client, how to find the appropriate Channel? We do not deal directly with the completion handler returned to the client, but the process needs to be transferred to another server and then return to send to the client.</p>
  
  <p>Before we use Channel.id () can be done, but Channel.id () has been removed, what alternative solutions do?With channel.hashcode () can?</p>