sichitong / robotics-networking Goto Github PK

Robotics networking stuff.

To install, run:

python2.7 setup.py install --user

This will make a user install. Make sure your environment sees executables in the local path.

If you're developing, use the following command:

python2.7 setup.py develop --user

Any changes you make will take effect immediately. No need to reinstall.

Then you can start the server using the following command (this is the executable that comes along with this library):

roboticsnet-server

And if you want to give a few things a shot manually, you can test with the client executable. You can run help to see what kind of commands are currently supported manually.

usage: roboticsnet-client [-h] [--forward FORWARD] [--reverse REVERSE]

[--forwardLeft FORWARDLEFT] [--queryproc] [--graceful] [--host HOST] [--port PORT] [--testall] [--startvid] [--stopvid]

optional arguments:

-h, --help	show this help message and exit
--forward FORWARD
	send forward command, given a value from 1 to 63
--reverse REVERSE
	send reverse command, given a value from 1 to 63
--forwardLeft FORWARDLEFT
	send forwardLeft command, given a value from 1 to 63

--forwardRight FORWARDRIGHT send forwardRight command, given a value from 1 to 63 --reverseLeft REVERSELEFT send reverseLeft command, given a value from 1 to 63 --reverseRight REVERSERIGHT send reverseRight command, given a value from 1 to 63 --queryproc send query about what is currently running --graceful shutdown server gracefully --host HOST specify an alternate host to default localhost --port PORT specify an alternate port to default 5000 --testall sends a command of each --startvid request video to start running --stopvid request video to stop running

So after running the server, with the above command (roboticsnet-server), you can send a packet this way:

$ roboticsnet-client --forward 23

Using port: 5000

Using host: localhost

Send move command...

Done!

And on the server side you should get the following:

Send things to motors

Received: 0x1 0x17

Make move command

Send things to motors

For the moment this is how things should look like:

It is possible to use this module without actually altering it. The way that this is done, is by providing hooks to the server's commands. The commands execute whenever there is a request that is received and processed. After the request is processed and matched against the proper command, the command is executed. Each command is associated with a hook. So after the command (pattern) is executed, the hook is executed right after.

There exists an example you can read in 'roboticsnet/examples/hook_example.py'.

We will go over segments of the above piece by piece in order for the reader to have an easier time understanding what is happening.

import roboticsnet
from roboticsnet.command_hook import CommandHook
from roboticsnet.rover_listener import RoverListener

def _forwardHook():
    ...

def _turnHook():
    ...

def _queryProcHook():
    ...

def _reverse=_reverseHook():
    ...

def _startVideo():
    ...

# First you would need to define your hooks using CommandHook
cmd_hook = CommandHook(
        forward=_forwardHook,
        turn=_turnHook,
        queryproc=_queryProcHook,
        reverse=_reverseHook,
        startVideo=_startVideoCount
        )

l = RoverListener(hooks=cmd_hook)
l.listen()

The above example starts a listening server with hooks. The 'def's prefixed with '_' are our cutsom hooks. We can provide any method we want in order to get this to execute arbitrary code. So for example, each time a 'forward' command is received, then the '_forwardHook()' method will actually execute once the request is done processing. This is how you attach your added, wanted behavior.

To do this we need an extra structure which stores this information (what hooks to execute whenever a particular command is received). We use an object called 'CommandHook', and set each of these hooks individually. You can omit hooks, and that will be fine - it simply means we do not want to bind any more behavior to a command.

You could also create classes, and pass their methods as hooks as well. Here is another example which is located in 'examples/hook_with_params.py'.

import roboticsnet
from roboticsnet.command_hook import CommandHook
from roboticsnet.rover_listener import RoverListener

forward_count = 0

class Counter:
    def __init__(self):
        self.count = 0

    def incr(self):
        self.count += 1

    def get(self):
        return self.count

def _forwardHook(params):
    print "This is my custom forward hook!"
    print "And in my custom forward hook, the params I receive are: ", params
    print "And I extract the value of interest: ", params['value']

def _turnHook():
    print "This is turn hook, where I don't care about the params (even though"
    print "we actually do receive params"

myCounter = Counter()

cmd_hook = CommandHook(
        forward=_forwardHook,
        turn=_turnHook,
        startVideo=myCounter.inrc
        )

l = RoverListener(hooks=cmd_hook)
l.listen()

print "The startvideo command was received this many times: ", myCounter.get()

That should conclude most of what you need to know about hooks!

Polling services have been added to the networking library. What this means is that you're able to pass code blocks, which will then be spawned as monitoring services.

The way this is achieved is by creating a monitoring service object which contains the code block you pass. It waits every specified time unit, and will then invoke the code block.

Essentially the code block you pass must return the value you need. How this ties all together in the end is that when the client will request for sensor info (see sensinfo in PROTOCOL), the networking library will go over all the monitoring services, and get the last value obtained from the polling. Then all of that information is packaged appropriately, and sent back to the client for consumption.

A sample file for these monitoring services may be found in

robotics-networking/examples/service_example.py

import roboticsnet
from roboticsnet.command_hook import CommandHook
from roboticsnet.rover_listener import RoverListener

forward_count = 0

def _forwardHook():
    global forward_count
    print "This is my custom forward hook!"
    forward_count += 1

def polling_service():
    """ Returns the same number all the time; for testing purposes """
    print "polling service 1 is executed!"
    return 42

def polling_service_2():
    """ Just another service """
    print "Service 2!"
    return 24

def cat():
    """ somehow a cat made it into the software! """
    print "MEW MEW MEW MEW"
    return 'cat'

# You don't need hooks in this case, but just to show that you can use them
# anyway.
cmd_hook = CommandHook(
        forward=_forwardHook
        )

l = RoverListener(\
        hooks=cmd_hook,
        # And again we bind the polling services here
        monitorProcs=[\
            polling_service,
            polling_service_2,
            cat])

print roboticsnet.__appname__, " ",  roboticsnet.__version__
print "Starting command dispatcher..."
l.listen()

print "The server is completely oblivious to the following information:"
print "  - forward commands received: ", forward_count