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.