Returns a specification to start this module under a supervisor.

See Supervisor.

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

args is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be (re)started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

• The GenServer is disabled by configuration but might be enabled later.
• An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

Launch a GenServer which starts a port and proxify cast and call to it using a port protocol with packet: 4, (32bits-length+data) messages are transmitted throught stdin/out. Input terms are encoded using binary_to_term and received terms are decoded using term_to_binary.

• cmd is the shell command to launch the port
• when the port starts, it automatically receives as first message the init term if init !== :no_init
• opts are options for Port.open (for instance [cd: "/path/"])
• link_opts are options for GenServer.start_link (for instance [name: :servername])
• messages received from the port outside of a GenServer.call context are sent to the event_manager GenEvent if it is not nil
• to allow easy supervision, if the port die with a return code == 0, then the GenServer die with the reason :normal, else with the reason :port_terminated