Sync/async data-flow communication

Prerequisites

By now, you should be an expert of the following components 😉:

• yarp::os::Port
• yarp::os::BufferedPort
• the main YARP command-line interfaces

Assignment

This assignment evaluates your understanding of sync/async data-flow communication in YARP. We want you to develop ...

1. Implement a module called producer with the following functionalities:

• has an output port (i.e. /producer/out)
• writes a random numbers to the port every 100ms
• has an argument called --async. If it is executed using --async switch, it should use the yarp::os::BufferedPort for streaming data otherwise it uses the yarp::os::Port

1. Implement another module called consumer with the following functionalities:

• has an input port (i.e. /consumer/in) to receive data from the producer and an output port (i.e. /consumer/out) to stream out some statistics
• reads from the input port and measures the data receiving rate (i.e. the time between to consecutive read). It should print out the received data to the terminal.
• it should stream out the measured data rate via its output port.
• has an argument called --delay. If it is executed, for example using --delay 1.0, it should wait for 1.0 second before performing the next read (i.e. introducing an arbitrary delay in reading)
• uses only yarp::os::Port

Scenario 1

• open a terminal and run the producer in sync mode (i.e., without any switch)

$ ./producer

• open another terminal and run the consumer without any switch

$ ./consumer

• connect the producer to the consumer using `tcp'

$ yarp connect /producer/out /consumer/in tcp

• read the measured data rate using yarp command , i.e. yarp read ... /consumer/out and see your measurement.
• repeat the above scenario using udp connection and/or BufferedPort (i.e. --async) to see if you notice any difference in data rate!

Scenario 2

In the second scenario, you should run another instance of consumer with the --delay 1.0 argument. To avoid the port name conflict, you can run the second consumer as follows. open another terminal and type:

$ YARP_PORT_PREFIX=/second ./consumer --delay 1.0

The YARP_PORT_PREFIX=/second environment variable simply adds a prefix (i.e. /second) to all the port which are opened by consumer. Thus to connect the producer to the second consumer you should type:

yarp connect /producer/out /second/consumer/in tcp

• At first use only tcp carrier for all the connections. Check the data rate measured by the first consumer (as the previous scenario) to see if there is any difference.
• repeat the scenario using 'udp' connections and see the difference.
• repeat the scenario, this time using Buffered port (i.e. running producer --async) for both tcp and udp connection and check the differences.

How to complete the assignment