Question

我有两个简单的组件，它们应该使用REQ / REP ZeroMQ模式相互通信。服务器（REP Socket）使用pyzmq：

在Python中实现

import zmq

def launch_server():
    print "Launching server"
    with zmq.Context.instance() as ctx:
        socket = ctx.socket(zmq.REP)
        socket.bind('tcp://127.0.0.1:5555')

        while True:
            msg = socket.recv()
            print "EOM\n\n"

使用NetMQ库用C＃编写的客户端（REQ套接字）：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NetMQ;


namespace PyNetMQTest
{
    class Program
    {

        static void Main(string[] args)
        {
            string msg;
            NetMQ.Sockets.RequestSocket socket = new NetMQ.Sockets.RequestSocket();
            socket.Connect("tcp://127.0.0.1:5555");
            for(int i=0; i<5; i++)
                socket.SendFrame("test_"+i);
        }
    }
}

通过与使用Python实现的REQ套接字交谈，Python Server实现已经过测试并且工作正常。但是C＃REQ套接字在循环的第一次迭代中抛出以下错误，并且没有任何消息到达服务器：

未处理的类型＆＃39; NetMQ.FiniteStateMachineException＆＃39;发生在NetMQ.dll中附加信息：Req.XSend - 无法发送其他请求

堆栈跟踪：

at NetMQ.Core.Patterns.Req.XSend(Msg& msg)
   at NetMQ.Core.SocketBase.TrySend(Msg& msg, TimeSpan timeout, Boolean more)
   at NetMQ.NetMQSocket.TrySend(Msg& msg, TimeSpan timeout, Boolean more)
   at NetMQ.OutgoingSocketExtensions.Send(IOutgoingSocket socket, Msg& msg, Boolean more)
   at NetMQ.OutgoingSocketExtensions.SendFrame(IOutgoingSocket socket, String message, Boolean more)
   at PyNetMQTest.Program.Main(String[] args) in d:\users\emes\documents\visual studio 2015\Projects\PyNetMQ Test\PyNetMQTest\Program.cs:line 20
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

这是我使用ZMQ的第一步，C＃代码来自库documentation。 是什么让代码抛出此错误？

我正在使用：

pyzmq 14.7
NetMQ 3.3.3.4
.NET 4.6

======================解决方案===================== =

正如@somdoron在他的回答中解释的那样，roor casue认为两个套接字都需要在发送/接收的整个周期之前才能重复使用。事实上，在python中实现的REP套接字并没有改变它的状态，因此错误在于python和C＃代码。这是固定代码：

REP Socket

import zmq

def launch_server():
    print "Launching server"
    with zmq.Context.instance() as ctx:
        socket = ctx.socket(zmq.REP)
        socket.bind('tcp://127.0.0.1:5555')

        while True:
            msg = socket.recv()
            socket.send("reply to "+msg)
            print "EOM\n\n"

REQ Socket

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NetMQ;


namespace PyNetMQTest
{
    class Program
    {

        static void Main(string[] args)
        {

            NetMQ.Sockets.RequestSocket socket = new NetMQ.Sockets.RequestSocket();
            socket.Connect("tcp://127.0.0.1:5555");

            string msg, reply;

            while (true)
            {
                Console.WriteLine("Type message: ");
                msg = Console.ReadLine();
                Console.WriteLine("Sending : " + msg);
                socket.SendFrame(msg);
                reply = socket.ReceiveFrameString();
                Console.WriteLine("Received: " + reply + Environment.NewLine);
            }
        }
    }
}

Answer 1

请求和响应套接字是状态机，请求必须先发送然后再调用Receive，不能连续调用5次发送。

如果响应相反，则必须先调用Receive。

如果一方只发送而另一方只接收您可以使用推拉模式而不是Req-Rep。如果需要两种方式通信，您也可以使用经销商 - 路由器。无论如何，似乎Req-Rep的使用是不正确的。

REQ / REP模式中的ZeroMQ FiniteStateMachineException

1 个答案: