Signal get_signal(ckt_time time): Quite simply, this method retrieves the signal which occurred at the specified time from the connector which feeds it by sending a get_signal() message to the port's encapsulated external connector. The get_signal() method will recurse through higher-level ports until a wire is reached; at which point, the signal list of the wire will be traversed and the desired signal, if found, will be returned.
Signal send_signal(Signal sig): This method is used to transmit the specified signal to the external connector of the port by sending the send_signal() message to the external connector. As with the get_signal() method, send_signal() will recurse through higher-level ports until the destination wire is reached. The signal will then be added to that wire. This method also propagates the signal to all the components in the fan-out of the port by invoking the propagate() member function which it inherited from its base Connector class.
void show_signals(): This method sends the show_signals() message to the external connector of the port in order to display all the signals that have passed through the port during the course of the simulation. As with the previous two methods, recursion will occur until a wire connector is reached, at which point the signal list of the wire will be traversed and displayed. This method is called by the show_outputs() method of the Component class.