C++ ZMQ经销商向自身发送和接收消息

我有一个zmq经销商插座，我正在连接到我机器上没有其他人连接的端口。我使用ZMQ_IMMEDIATE选项来阻止套接字在没有连接对等方的情况下发送消息。如果我尝试发送一条消息足够多次（大约五分钟），最终我能够发送消息并接收到一条与我试图发送的大小和数据相同的消息

使用zmq_socket_监视器最终显示经销商插座能够连接并向自身发送/接收消息。有人能解释为什么会这样吗

#include <unistd.h>
#include <iostream>
#include <zmq.hpp>
#include <thread>
#include <sstream>
static int read_msg(void* s, zmq_event_t* event, char* ep)
{
 int rc ;
 zmq_msg_t msg1; // binary part
 zmq_msg_init (&msg1);
 zmq_msg_t msg2; // address part
 zmq_msg_init (&msg2);
 rc = zmq_msg_recv (&msg1, s, 0);
 if (rc == -1 && zmq_errno() == ETERM)
 return 1 ;
 assert (rc != -1);
 assert (zmq_msg_more(&msg1) != 0);
 rc = zmq_msg_recv (&msg2, s, 0);
 if (rc == -1 && zmq_errno() == ETERM)
 return 1;
 assert (rc != -1);
 assert (zmq_msg_more(&msg2) == 0);
 // copy binary data to event struct
 const char* data = (char*)zmq_msg_data(&msg1);
 memcpy(&(event->event), data, sizeof(event->event));
 memcpy(&(event->value), data+sizeof(event->event), sizeof(event->value));
 // copy address part
 const size_t len = zmq_msg_size(&msg2) ;
 ep = (char*)memcpy(ep, zmq_msg_data(&msg2), len);
 *(ep + len) = 0 ;
 return 0 ;
}


// dealer socket monitor thread
static void *dealer_socket_monitor (void *ctx)
{
 zmq_event_t event;
 static char addr[1025] ;
 int rc;

 printf("starting monitor...\n");

 void *s = zmq_socket (ctx, ZMQ_PAIR);
 assert (s);
 int num = 0;
 rc = zmq_connect (s, "inproc://monitor.dealer");
 assert (rc == 0);
 while (!read_msg(s, &event, addr)) {
 switch (event.event) {
 case ZMQ_EVENT_CONNECT_RETRIED:
 printf (" DEALER connect retried socket descriptor %d %d\n", event.value, num);
 printf (" DEALER connect retried socket address %s\n", addr);
 break;
 case ZMQ_EVENT_CONNECT_DELAYED:
 printf (" DEALER connect delayed socket descriptor %d %d\n", event.value, num);
 printf (" DEALER connect delayed socket address %s\n", addr);
 break;
 case ZMQ_EVENT_LISTENING:
 printf (" DEALER listening socket descriptor %d %d\n", event.value, num);
 printf (" DEALER listening socket address %s\n", addr);
 break;
 case ZMQ_EVENT_CONNECTED:
 printf (" DEALER connected socket descriptor %d %d\n", event.value, num);
 printf (" DEALER connected socket address %s\n", addr);
 break;
 case ZMQ_EVENT_MONITOR_STOPPED:
 printf (" DEALER monitor ending socket descriptor %d %d\n", event.value, num);
 printf (" DEALER monitor ending socket address %s\n", addr);
 break;
 case ZMQ_EVENT_ACCEPTED:
 printf (" DEALER accepted socket descriptor %d %d\n", event.value, num);
 printf (" DEALER accepted socket address %s\n", addr);
 break;
 case ZMQ_EVENT_CLOSE_FAILED:
 printf (" DEALER socket close failure error code %d %d\n", event.value, num);
 printf (" DEALER socket address %s\n", addr);
 break;
 case ZMQ_EVENT_CLOSED:
 printf (" DEALER closed socket descriptor %d %d\n", event.value, num);
 printf (" DEALER closed socket address %s\n", addr);
 break;
 case ZMQ_EVENT_DISCONNECTED:
 printf (" DEALER disconnected socket descriptor %d %d\n", event.value, num);
 printf (" DEALER disconnected socket address %s\n", addr);
 break;
 default:
 printf(" DEALER default case\n");
 }
 }
 zmq_close (s);
 return NULL;
}
int main() {
     pthread_t thread ;
    std::string connect = "tcp://localhost:49150";
    zmq::context_t context(1);
    zmq::socket_t client (context, ZMQ_DEALER);
    int m_linger = 0;
    int count = 0;
    int m_timeoutMs = 1000;
    int imm = 1;
    // release the socket / port asa it disconnects
    client.setsockopt(ZMQ_LINGER, &m_linger, sizeof(m_linger));
    client.setsockopt(ZMQ_RCVTIMEO, &m_timeoutMs, sizeof(m_timeoutMs));
    client.setsockopt(ZMQ_SNDTIMEO, &m_timeoutMs, sizeof(m_timeoutMs));
    client.setsockopt(ZMQ_IMMEDIATE, &imm, sizeof(imm));

    client.connect(connect.c_str());
    std::cout << "Connecting client to " << connect << std::endl;

     // socket monitoring
    int rc = zmq_socket_monitor ((void*)client, "inproc://monitor.dealer", ZMQ_EVENT_ALL);
    rc = pthread_create (&thread, NULL, dealer_socket_monitor, (void*)context);
    int more = 0;
    while(true)
    {
        zmq::message_t blank{};
        zmq::message_t message(sizeof(int));
        zmq::message_t response;
        int more; //  Multipart detection
        std::cout << "Client no linger sending message more enabled" << std::endl;
        auto ret = client.send(blank, ZMQ_SNDMORE);
        if (!ret)
        {
            std::cout << "timeout on send, trying again" << std::endl;
            continue;
        }
        std::cout << "Client no linger sending message more disabled" << std::endl;
        ret = client.send(message);
        if (!ret)
        {
            std::cout << "timeout on send second, trying again";
            continue;
        }
        ret = client.recv(&response);
        size_t more_size = sizeof (more);
        client.getsockopt(ZMQ_RCVMORE, &more, &more_size);
        while (more)
        {
            std::cout << "Client received message with more coming. Size of message " << response.size() << std::endl;
            client.recv(&response);
            client.getsockopt(ZMQ_RCVMORE, &more, &more_size);
        }
        std::cout << "Client received final part of message. Size of message " << response.size() << " message " << *(reinterpret_cast<int*>(message.data())) << std::endl;
        exit(0);
    }
}

GCC 6.3使用：g++-std=c++11 client.cpp-o client-g-lzmq-lpthread编译 cppzmq-devel 4.1.4-6和zmq 4.1.4-6

我与nodej有一个接口，套接字最终会连接到自己。这里似乎也发生了同样的情况：ZeroMQ套接字创建了一个本地临时端口，该端口与您要连接的端口相同（49150）

如果是这样，当您连接到没有服务正在侦听的保留端口（<1024）时，不应该发生这种情况，例如端口7。绑定/侦听临时端口范围之外的端口（Linux上小于32768）应该可以解决此问题

---

使用诸如使用

netstat

或

tcpdump

/

wireshark

之类的工具来检查这实际上是在套接字/网络级别发生的。

@LightnessRacesinOrbit我将我的帖子编辑成更像是一个答案，而不是评论。我很确定这是实际问题。我的队友发现了同样的问题，经销商渠道会以10分钟或更长的时间间隔连接到自身，使用的端口范围在51xxx范围内，在阅读此答案后，他将端口范围更改为21xxx，不再有问题，他表示感谢。他会自己评论，但StackOverflow point系统阻止他评论。

 DEALER closed socket descriptor 10 0
 DEALER closed socket address tcp://localhost:49150
 DEALER connect retried socket descriptor 185 0
 DEALER connect retried socket address tcp://localhost:49150
 DEALER connect delayed socket descriptor 115 0
 DEALER connect delayed socket address tcp://localhost:49150
 DEALER connected socket descriptor 10 0
 DEALER connected socket address tcp://localhost:49150
Client no linger sending message more disabled
Client received message with more coming. Size of message 0
Client received final part of message. Size of message 4 message 0