How to set up a ZeroMQ request-reply between a c# and python application

Question

I'm trying to communicate between a c#(5.0) and a python (3.9) application via ZeroMQ. For .Net I'm using NetMQ and for python PyZMQ.

I have no trouble letting two applications communicate, as long as they are in the same language

• c# app to c# app;
• python -> python;
• java -> java,

but trouble starts when I try to connect between different languages.

• java -> c# and reverse works fine as well [edited]

I do not get any errors, but it does not work either.

I first tried the PUB-SUB Archetype pattern, but as that didn't work, I tried REQ-REP, so some remainders of the "PUB-SUB"-version can still be found in the code.

My Python code looks like this :

def run(monitor: bool):
loop_counter: int = 0

context = zmq.Context()
# socket = context.socket(zmq.PUB)
# socket.bind("tcp://*:5557")
socket = context.socket(zmq.REP)
socket.connect("tcp://localhost:5557")

if monitor:
    print("Connecting")

# 0 = Longest version, 1 = shorter version, 2 = shortest version
length_version: int = 0

print("Ready and waiting for incoming requests ...")

while True:
    message = socket.recv()

    if monitor:
        print("Received message:", message)

    if message == "long":
        length_version = 0
    elif message == "middle":
        length_version = 1
    else:
        length_version = 2

    sys_info = get_system_info(length_version)

    """if not length_version == 2:
        length_version = 2

    loop_counter += 1

    if loop_counter == 15:
        length_version = 1

    if loop_counter > 30:
        loop_counter = 0
        length_version = 0"""

    if monitor:
        print(sys_info)

    json_string = json.dumps(sys_info)
    print(json_string)
    socket.send_string(json_string)

My C# code :

static void Main(string[] args)
    {
        //using (var requestSocket = new RequestSocket(">tcp://localhost:5557"))
        using (var requestSocket = new RequestSocket("tcp://localhost:5557"))    
        {
            while (true) {
                Console.WriteLine($"Running the server ...");
                string msg = "short";
                requestSocket.SendFrame(msg);
                var message = requestSocket.ReceiveFrameString();
                Console.WriteLine($"requestSocket : Received '{message}'");
                //Console.ReadLine();
                Thread.Sleep(1_000);
            }
        }
    }

Answer 1

Seeing the period of your problems maybe it's because of versions. I run fine a program for long time with communications from Windows/C# with NTMQ 4.0.0.207 239,829 7/1/2019 on one side and Ubuntu/Python with zeromq=4.3.1 and pyzmq=18.1.0. I just tried updating to use same NETMQ version but with new versions zeromq=4.3.3 and pyzmq=20.0.0 but there is a problem/bug somewhere and it doesn't run well anymore.

So your code doesn't look bad may be it's software versions issues not doing well try with NTMQ 4.0.0.207 on c# side and zeromq=4.3.1 with pyzmq=18.1.0 on python side