Add new Subscription to Rocket chat

Question

I want to create a new subscription e.g (stream-all-messages) in Rocket Chat same as stream-room-messages which is already present in docs.

I am using DDP listener to test it, following are the examples which I am trying.

// Subscribe to a message stream from a channel or group
console.log("Attempting to subscribe to the Group/Channel now.\n");
ddpClient.subscribe("stream-room-messages", [RoomId, false], function() {
  console.log(ddpClient.collections);
  console.log("Subscription Complete.\n");
  // Display the stream on console so we can see its working
  console.log("\nStarting live-stream of messages.:\n");
  ddpClient.on("message", function(msg) {
    console.log("Subscription Msg: " + msg);
  });
});

above example works because stream-room-messages already present but when I try to execute the following it raises an error i.e.

Subscription Msg: {"msg":"nosub","id":"2","error":{"isClientSafe":true,"error":404,"reason":"Subscription 'stream-only-messages' not found","message":"Subscription 'stream-all-messages' not found [404]","errorType":"Meteor.Error"}}

when I call this

// Subscribe to a message stream from a channel or group
console.log("Attempting to subscribe to the Group/Channel now.\n");
ddpClient.subscribe("stream-all-messages", [RoomId, false], function() {
  console.log(ddpClient.collections);
  console.log("Subscription Complete.\n");
  // Display the stream on console so we can see its working
  console.log("\nStarting live-stream of messages.:\n");
  ddpClient.on("message", function(msg) {
    console.log("Subscription Msg: " + msg);
  });
});

Please help me out how can I add a new subscription.