How to create a thing

What will the thing do for us?

We will create a thing which sends mails if it gets a message from a specific driver from a specific node with a specific body. All other messages, which will come this node will be logged with a warning.

Before we can send the email, we have to initialize the driver, because we have to start an external application. This will be done in the init function.

Note: For sending the emails we will use gen_smtpc which is a simple mail client.

Ok, let's start

1. Create a new module in the app/horst/src directory.

-module(mail_client_driver).

-export([init/1,handle_msg/3]).

init(Config) ->
	lager:info("mail_client_driver:init('~p')", [Config]),	
	application:start(gen_smtpc).

handle_msg([Node ,Sensor, Id, Time, Body], Config, Module_config) ->
	Config.

2. Edit the things.config and add the new driver

The things.config is the configuration file where you can enable/disable and configure your things.

{thing, "Mail_Client", 
	[
	{type, actor}, 
	{driver, {mail_client_driver, handle_msg}, [{init, true, [{options, [{use_ssl, true}, {host, "smtp.gmail.com"}, {port, 465}]}]}]},
	{activ, true},
	{timer, 0},
	{database, []},
	{description, "Mail Client for sending notification."}
	]}.

The new thing is named "Mail_Client". The name must be unique in your enviroment. The thing is from type actor. The driver tag describes the your thing. You can read like this: The driver is implemented in the module mail_client_driver and entry function is handle_msg. Note: it is implicit that you have 3 arguments. The arguments are: Message, Config, Module-Config.

Here, the module config contains the following elements :

• init true means that we need a init function inside our driver and that it will be called during init phase.
• options [list of parameters] These option are passed to gen_smtpc application when we send an email.

The timer is not used The database is not used The description contains only text which describes the thing.

Now we can go into the horst directory and compile everthing.

ua@ua-TA880GB:~/Dropbox/projects/erlang/sensor/horst$ make
==> goldrush (compile)
==> lager (compile)
==> gpio (compile)
==> erlib (compile)
==> sue (compile)
==> gen_smtpc (compile)
Compiled src/gen_smtpc_app.erl
Compiled src/gen_smtpc_sup.erl
Compiled src/gen_smtpc.erl
==> horst (compile)
==> horst (compile)

if you don't get any error you can start horst by typing:

ua@ua-TA880GB:~/Dropbox/projects/erlang/sensor/horst$./dev.sh

In the log output you will see that the init function of the mail_client_driver is called and that the gen_smtpc application is started.

mail_client_driver:init('[{options,[{use_ssl,true},{host,"smtp.gmail.com"},{port,465}]}]')
08:58:40.517 [info] Application horst started on node 'horst@ua-TA880GB' gen_smtpc_sup started ...