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）是使用 pyzmq 在 Python 中实现的：
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);
}
}
}
Python 服务器实现已经过测试，通过与使用 Python 实现的 REQ 套接字通信，可以正常工作。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：
NetMQ.dll 中发生“NetMQ.FiniteStateMachineException”类型的未处理异常
附加信息：Req.XSend - 无法发送另一个请求
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# 代码取自库文档 http://netmq.readthedocs.io/en/latest/introduction/. 是什么让代码抛出这个错误？
我在用：
- pyzmq 14.7
- NetMQ 3.3.3.4
- .NET 4.6
====================== 解决方案======================
正如 @somdoron 在他的回答中所解释的，原因是两个套接字都需要经过完整的发送/接收周期才能被重用。
事实上，在 python 中实现的 REP 套接字也从未改变过它的状态，因此错误同时存在于 python 和 C# 代码中。这是固定代码：
REP插座
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"
请求套接字
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)
{
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);
}
}
}
}
