When listening to the stream on the server or client, you could be able to access some of the useful information from the listening method. For an example, you can get the userId of the sender as follows.

if(Meteor.isClient) {
  stream = new Meteor.Stream('hello');
  stream.on('message', function(content) {
    var userId = this.userId; 
    console.log('sending user is: ', userId);
  });
}

As you can see, there are few useful information available in the this context variable.

In the client side listening method

You can see following fields with this context.

• userId - if the sender is loggedin his userId or otherwise null
• subscriptionId - unique id of the sending client

In the server side listening method

You can see following fields with this context.

• userId - if the sender is loggedin his userId or otherwise null
• subscriptionId - unique id of the sending client
• onDisconnect - you can assign a callback to this to get notified after the client get disconnected from the server

In filters

You can see following fields with this context.

• userId - if the sender is loggedin his userId or otherwise null
• subscriptionId - unique id of the sending client