ZeroMQ 在 Unity 中不起作用，但可以作为控制台应用程序使用

Question

I try to connect my python process with Unity game through ZeroMQ. I have a python script server.py which sends a message through pair socket

import zmq

context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.bind(f"tcp://*:5556")

socket.send(b"Server message to client")
print("Sent")

And I have a MonoBehaviour script attached to a GameObject within Unity, which looks like this:

public class AiManager : MonoBehaviour
{
    void Start()
    {
        using (var server = new PairSocket())
        {
            server.Connect("tcp://localhost:5556");
            var msg = server.ReceiveFrameString();
            Debug.Log(msg);
        }
    }
}

The game hangs on ReceiveFrameString() forever and crashes Unity. Also server.py hangs and doesn't send the message.

However I created an independent console application, with the exact same code:

class Program
{
    static void Main(string[] args)
    {
        using (var server = new PairSocket())
        {
            server.Connect("tcp://localhost:5556");
            var msg = server.ReceiveFrameString();
            Console.WriteLine($"From Server: {msg}");
        }
    }
}

This application works perfectly.

How can I fix that?

Answer 1

It can be a total PITA ensuring that Unity (ie, the Unity app) simply has permission to talk locally.

I assume you're on PC, not Mac, examine carefully if Unity is allowed to make such network connections.

Windows firewall settings can be a total PITA for Unity.

Read various threads, https://forum.unity.com/threads/solved-multiplayer-networking-lan-wont-connect-from-another-pc.470459/

One solution is, spin up a real remote server on AWS, and try that. It's often easier than getting localhost to work.

One shitty problem is that quite simply, on some versions of Windows the stupid "OK" dialog which appears actually appears behind Unity, doh, can waste hours.

Answer 2

Alright, after multiple hours of experimenting and browsing the internet I have fixed the problem.

First thing to do, thanks to @jdweng's comment is to first send a message from client to server.

Server doesn't do anything when a connection is made. The server is a slave and waits for a client to send a command. [...] It behaves differently as console application, because you are dealing with a different kernel/operating system with different drivers.

Adding a server.SendFrameEmpty(); to the client and socket.recv() to the server fixes the problem, but Unity still freezes.

I found this answer saying:

The key is to have AsyncIO.ForceDotNet.Force(); before you start and NetMQConfig.Cleanup(); before you end.

Finally the whole working code looks like this

public class AiManager : MonoBehaviour
{
    void Start()
    {
        AsyncIO.ForceDotNet.Force();
        using (var server = new PairSocket())
        {
            server.Connect("tcp://localhost:5556");
            server.SendFrameEmpty();
            var msg = server.ReceiveFrameString();
            Debug.Log(msg);
        }
        NetMQConfig.Cleanup();
    }
}