def zmq_import_poll(sock: zmq.Socket, timeout: float):
"""
Author:
Alexander Heilmeier
Description:
Handles incoming ZMQ messages and allows polling.
Inputs:
sock: ZMQ socket (see below how to create it)
timeout: [s] timeout for polling
How to create a ZMQ socket to import data?
import zmq
zmq_context = zmq.Context()
sock = zmq_context.socket(zmq.PUB)
sock.connect("tcp://%s:%s" % (ip, port))
sock.setsockopt_string(zmq.SUBSCRIBE, zmq_topic])
"""
# ------------------------------------------------------------------------------------------------------------------
# PREPARATION ----------------------------------------------------------------------------------------------------
# ------------------------------------------------------------------------------------------------------------------
# timeout conversion s -> ms
timeout *= 1000.0
# set standard return
data = None
# ------------------------------------------------------------------------------------------------------------------
# CHECK IF BUFFER ALREADY STORES VALUES ----------------------------------------------------------------------------
# ------------------------------------------------------------------------------------------------------------------
# non blocking socket to empty buffer
try:
while True:
sock.recv_string(flags=zmq.NOBLOCK)
data = sock.recv_pyobj(flags=zmq.NOBLOCK)
except zmq.Again:
pass
# ------------------------------------------------------------------------------------------------------------------
# WAIT FOR A SHORT TIME IF NO DATA WAS STORED IN THE BUFFER --------------------------------------------------------
# ------------------------------------------------------------------------------------------------------------------
if data is None:
# use poll to be able to set a timeout -> will return 1 if an event occurs, otherwise 0
events = sock.poll(timeout=timeout)
if events:
# non blocking socket to empty buffer
try:
while True:
sock.recv_string(flags=zmq.NOBLOCK)
data = sock.recv_pyobj(flags=zmq.NOBLOCK)
except zmq.Again:
pass
return data
def recv_json(socket: zmq.Socket, **kw) -> Dict:
"""
Receive a dictionary.
"""
s_data = socket.recv_string(**kw)
return json.loads(s_data)
def zmq_import(sock: zmq.Socket,
blocking: bool = False,
datatype: str = "pyobj",
use_buffer: bool = False):
"""
Author:
Alexander Heilmeier & Tim Stahl
Description:
Handles incoming ZMQ messages.
Inputs:
sock: ZMQ socket (see below how to create it)
blocking: set if socket should be blocking (i.e. wait until new message is received) or not
datatype: string that indicates if it should be received as Python object (pyobj), json (json) or string (str)
use_buffer: flag to indicate if the buffer should be returned completely (True) or only the latest message (False)
Hint: Conversion of json objects to their original data type is handled by PyZMQ and therefore must not be done by
hand.
How to create a ZMQ socket to import data?
import zmq
zmq_context = zmq.Context()
sock = zmq_context.socket(zmq.PUB)
sock.connect("tcp://%s:%s" % (ip, port))
sock.setsockopt_string(zmq.SUBSCRIBE, zmq_topic])
"""
# ------------------------------------------------------------------------------------------------------------------
# Specify called receive handle ------------------------------------------------------------------------------------
# ------------------------------------------------------------------------------------------------------------------
if datatype == "pyobj":
sock_recv_fct = lambda **kwargs: sock.recv_pyobj(**kwargs)
elif datatype == "json":
sock_recv_fct = lambda **kwargs: sock.recv_json(**kwargs)
elif datatype == "str":
sock_recv_fct = lambda **kwargs: sock.recv_string(**kwargs)
else:
raise RuntimeError("Specified datatype is not supported!")
# ------------------------------------------------------------------------------------------------------------------
# FUNCTION BODY ----------------------------------------------------------------------------------------------------
# ------------------------------------------------------------------------------------------------------------------
data = None
buffer = []
# non blocking socket to empty buffer
try:
while True:
sock.recv_string(flags=zmq.NOBLOCK)
data = sock_recv_fct(flags=zmq.NOBLOCK)
if use_buffer:
buffer.append(data)
except zmq.Again:
pass
# if no data was received above and blocking is True, wait for new data
if blocking and not use_buffer and data is None:
sock.recv_string()
data = sock_recv_fct()
elif blocking and use_buffer and not buffer:
sock.recv_string()
data = sock_recv_fct()
buffer.append(data)
if use_buffer and buffer:
return buffer
elif use_buffer:
return None
else:
return data
def recv_string(socket: zmq.Socket, **kw) -> str:
"""
Receive a string.
"""
return socket.recv_string(**kw)
