TISM can manage 16 inputs and 16 outputs. Each of them is defined by a port number (0-15).
A protocol and its parameters are associated to each port.
When a message is receive on a port, the first value is set to the input port number.
In the same way, the first value of an outgoing message defines the port on which the message is going to be emitted. If a message format doesn't fit with the protocol, it's discarded.