YARP producer consumer with Port and BufferedPort

This tutorial helps you understand the behavior of yarp::os::Port versus yarp::os::BufferedPort.

To deepen your undrstanding of these classes you may checkout the online documentation and their APIs:

• yarp::os::Port
• yarp::os::BufferedPort

Build and Install the code

Follow these steps to build and properly install your module:

$ cd tutorial_yarp-producer-consumer
$ mkdir build; cd build
$ cmake ../
$ make
$ make install

What this code does

The code will generate producer consumer pairs using conventional yarp::os::Port and yarp::os::BufferedPort.

The producer opens a port /producer, in which it sends numbered messages. The consumer opens a port /consumer, in which it receives data, and it prints the content at the console.

Terminal 1: Start the yarp server if not already running.

$ yarpserver

Terminal 2: run the producer

$ tutorial_yarp-producer-port
yarp: Port /producer active at tcp://10.255.36.11:10097/
[1] written message
[2] written message
[3] written message
[4] written message

Terminal 3: Run the consumer

$./tutorial_yarp-consumer-port 
yarp: Port /consumer active at tcp://10.255.36.11:10098/

Terminal 4: Connect /producer to /consumer

$ yarp connect /producer /consumer

The consumer should show something like this:

yarp: Receiving input from /producer to /consumer using tcp
Received: 20 Hello from producer
Received: 21 Hello from producer
Received: 22 Hello from producer
Received: 23 Hello from producer
Received: 24 Hello from producer

Terminal 5: Now run another instance of consumer, specify a different port name and add a delay.

$./tutorial_yarp-consumer-port --name /consumer2 --delay 5000

Now you have a second consumer. To simulate a slow computer we added a delay (5s), which is the time the consumer waits before reading from the port.

Terminal 6: Connect the second consumer to the producer

yarp connect /producer /consumer2

What happens to the producer? What happens when you disconnect one of the consumers?

Try connecting using a different protocol (i.e. udp):

yarp connect /producer /consumer2 udp
yarp connect /producer /consumer udp

Now replicate the same experiment, this time using yarp::os::BufferedPort, i.e. tutorial_yarp-producer-buff and tutorial_yarp-consumer-buff.

Further reading

Behavior of YARP ports is detailed in the following documents:

• Buffering Policies with YARP