YARP companion basics

This is informal, tutorial-style section meant to give the flavor of using YARP.

First, please open two terminal windows; we'll refer to these as A and B. Before doing any communication, is is necessary to start the YARP name service – this is a program which keeps track of what YARP resources are currently available and how to access them. In terminal A, type:

yarp server

If all goes well, you will see the message yarp: name server starting at ...'' -- if not, check any configuration file mentioned in the output ofyarp conf''. Next, in terminal B, type:

yarp check

This will try to communicate with the name server, send a message, receive a message, and basically make sure that everything is working well. Here is what you should see:

==================================================================
=== Trying to register some ports
yarp: Registered port ... as tcp://5.255.112.225:10011
yarp: Registered port ... as tcp://5.255.112.225:10001
==================================================================
=== Trying to connect some ports
yarp: /tmp/port/2: Receiving input from /tmp/port/1 to /tmp/port/2 using tcp
yarp: Sending output from /tmp/port/1 to /tmp/port/2 using tcp
==================================================================
=== Trying to write some data
==================================================================
=== Trying to read some data
*** Read number 42
==================================================================
=== Trying to close some ports
yarp: Shutting down port /tmp/port/2
yarp: /tmp/port/2: Stopping input from /tmp/port/1 to /tmp/port/2
yarp: stopping output from /tmp/port/1 to /tmp/port/2
yarp: Shutting down port /tmp/port/1
*** YARP seems okay!

Here is an example of things going wrong:

==================================================================
=== Trying to register some ports
yarp: Couldn't connect to 5.255.112.225
yarp: Name server missing

If networking is broken on your machine, then YARP will have trouble. If you are running the YARP name server on a machine that does not have a static IP address or a name registered with DNS, then you should check the configuration file mentioned by `‘yarp where’', and make sure that the first line of the configuration file is of the form:

  current.valid.ip.address 10000

The number `‘10000’' is the default port number that the YARP name service uses. This is usually fine; if you have a conflict with this, then please change it in the configuration file.

If all is well, we can try exercising YARP a little more.

In terminal B, type:

yarp read /port1

This will report `‘yarp: Registered port /port1 ...’' in terminal B and in terminal A some corresponding message will also appear. Next, in terminal C, type:

yarp write /port2

If all goes well, this will report `‘yarp: Registered port /port2 ...’' in terminal C and in terminal A some corresponding message will also appear. Now, in terminal D, type:

yarp connect /port2 /port1

Terminal C will report Connecting /port2 to /port1''. Now if you typehello world'' into terminal C, and hit enter, that text will appear on terminal B.

If everything is going okay so far, type on terminal E:

yarp read /port3

and on terminal D, type:

yarp connect /port2 /port3

Now any line you enter in terminal C should appear in both terminal B and E.

YARP companion advanced

For more advanced uses see yarp: the main YARP command-line interface

Table of Contents

YARP companion basics

YARP companion advanced