Services tutorial service socket

MORSE has a concept of services: services are remote procedure calls commonly used to configure or control the simulation’s behaviour.

This tutorial shows how to use these services. Different middlewares are supported; refer to the Middleware support in MORSE (search requests in the Features compatibility matrix).

Pre-requisites

• You must have completed the first tutorial.

Using the services

In order to use a service, you must know the exact name of this service, and its parameters (You can refer to the component page, available here).

Here is an example using a human component (the services available are documented here).

Scene description

Let’s start to describe the Morse scene. Here, the interesting part is that we activate the service for human using the add_service method.

from morse.builder import *

human = Human()
human.add_service('socket')
env = Environment('empty', fastmode=True)

Controlling the human with telnet

Now, let’s see how we can control it using telnet:

$ telnet localhost 4000
    Trying 127.0.0.1...
    Connected to localhost.localdomain.
    Escape character is '^]'.
> id1 human move [0.1, 0.0]
    id1 SUCCESS

where id1 is the arbitrary id of the request, human is the name of the used component, move and [0.1 ,0.0] are respectively the name of the request and its parameters. This parameters must be in a JSON list.

Controlling the human with socket socket

Here is a simple example of using services with sockets in Python (available at $MORSE_ROOT/tools/simple_exemple.py):

import sys
import socket
import tty, termios

HOST = '127.0.0.1'
PORT = 4000

def getchar():
        """ Returns a single character from standard input """

        fd = sys.stdin.fileno()
        old_settings = termios.tcgetattr(fd)
        try:
                tty.setraw(sys.stdin.fileno())
                ch = sys.stdin.read(1)
        finally:
                termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
        return ch


def _connect_port(port):
        """ Establish the connection with the given MORSE port"""
        sock = None

        for res in socket.getaddrinfo(HOST, port, socket.AF_UNSPEC, socket.SOCK_STREAM):
                af, socktype, proto, canonname, sa = res
                try:
                        sock = socket.socket(af, socktype, proto)
                except socket.error:
                        sock = None
                        continue
                try:
                        sock.connect(sa)
                except socket.error:
                        sock.close()
                        sock = None
                        continue
                break

        return sock

def main():
        sock = _connect_port(PORT)
        if not sock:
                sys.exit(1)

        print("socket connected")
        print("Please press q to quit and use 8456 to move")
        esc = 0
        _id = 0

        while not esc:
                c = getchar()
                speed = 0
                rot = 0
                if (c == "8"):
                        speed = 0.1
                elif (c == "5"):
                        speed = -0.1
                elif (c == "4"):
                        rot = 0.1
                elif (c == "6"):
                        rot = -0.1
                if (speed != 0 or rot != 0):
                        data_out = "id%d human move [%f, %f]\n" % (_id, speed, rot)
                        sent = sock.send(data_out)
                        print ("SENT DATA (%d bytes): %s" % (sent, data_out))
                        _id = _id + 1

                if c == "q":
                        esc = 1

        sock.close()
        print("\nBye bye!")

main()

Note

You can find a more complete example of a Python file using services to move the human here: $MORSE_ROOT/tools/wiimote_human_client.py. (using wiimote to control the human)

Controlling the human with pymorse pymorse

The previous example can be rewritten more easily using the pymorse API.

import sys
import tty, termios
from pymorse import Morse

def getchar():
        """ Returns a single character from standard input """

        fd = sys.stdin.fileno()
        old_settings = termios.tcgetattr(fd)
        try:
                tty.setraw(sys.stdin.fileno())
                ch = sys.stdin.read(1)
        finally:
                termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
        return ch

def main():
        with Morse()  as  morse:
                print("Please press q to quit and use 8456 to move")
                esc = 0

                while not esc:
                        c = getchar()
                        speed = 0
                        rot = 0
                        if (c == "8"):
                                speed = 0.1
                        elif (c == "5"):
                                speed = -0.1
                        elif (c == "4"):
                                rot = 0.1
                        elif (c == "6"):
                                rot = -0.1
                        if (speed != 0 or rot != 0):
                                morse.rpc('human', 'move', speed, rot)

                        if c == "q":
                                esc = 1

                print("\nBye bye!")

main()

Creating the Service

Please, refer to Services in MORSE.