Websocket Subscriptions

Before we can subscribe to any changes, we first need to ask for access to the database-api with

> {"id":2,"method":"call","params":[0,"database",[]]}
< {"id":2,"result":1}

The result will be our DATABASE_API_ID!

In Graphene, we have the following subscriptions available:

• set_subscribe_callback( cb, bool clear_filter ): To simplify development a global subscription callback can be registered.
• set_pending_transaction_callback( cb ): Notifications for incoming unconfirmed transactions.
• set_block_applied_callback( blockid ): Gives a notification whenever the block blockid is applied to the blockchain. Let's first get a global scubscription callback to disctinguish our notifications from regular RPC calls:

> {"id":4,"method":"call","params":[DATABASE_API_ID,"set_subscribe_callback",[SUBSCRIPTION_ID]]}

This call above will register SUBSCRIPTION_ID as id for notifications.

Now, whenever you get an object from the witness (e.g. via get_objects) you will automatically subscribe to any future changes of that object.

After calling set_subscribe_callback the witness will start to send notices every time the object changes:

< {
    "method": "notice"
    "params": [
        SUBSCRIPTION_ID, 
        [[
            { "id": "2.1.0", ...  },
            { "id": ...  },
            { "id": ...  },
            { "id": ...  }
        ]]
    ], 
}

Here is an example of a full session:

> {"id":1,"method":"call","params":[0,"login",["",""]]}
< {"id":1,"result":true}
> {"id":2,"method":"call","params":[0,"database",[]]}
< {"id":2,"result":1}
> {"id":3,"method":"call","params":[1,"set_subscribe_callback",[200]]}
< {"id":3,"result":true}
< {"method":"notice","params":[200,[[{"id":"2.1.0","random":"2033120557c36e278db2eaad818494f791ff4d7b0418858a7ab9b5a8","head_block_number":5,"head_block_id":"00000005171f82f1b6bd948e7d58d95e572001fd","time":"2015-05-01T13:05:50","current_witness":"1.7.5","next_maintenance_time":"2015-05-02T00:00:00"}]]]}
< {"method":"notice","params":[200,[[{"id":"2.1.0","random":"9d5ff7e453db4815005eb42ddd040e3afb459950f75f4440deb3dec0","head_block_number":6,"head_block_id":"000000060e3369d6feaf330ea9114cd855c93aab","time":"2015-05-01T13:05:55","current_witness":"1.7.3","next_maintenance_time":"2015-05-02T00:00:00"}]]]}
< {"method":"notice","params":[200,[[{"id":"2.1.0","random":"cb8686582c40634a0c0834d0f2c4ad19f8ca80598cc3eee2b93c124d","head_block_number":7,"head_block_id":"000000071d0bc8db55d7da75d1d880818d1930fd","time":"2015-05-01T13:06:00","current_witness":"1.7.0","next_maintenance_time":"2015-05-02T00:00:00"}]]]}