断开 ZeroMQ 套接字和 ZMQ_EVENT_DISCONNECTED

问题描述

ZeroMQ API documentation 声明事件（来源 here）：

ZMQ_EVENT_DISCONNECTED
插座意外断开。事件值是底层网络套接字的 FD。警告：此套接字将被关闭。

此处如何定义“意外”，以及如何在 REQ-REP 对上触发“干净”断开连接？

我试过了：

• zmq_close(client) 表示 ZMQ_EVENT_DISCONNECTED，虽然我原以为这是干净的
• zmq_disconnect(client,addr) 在上述不会改变被监控事件之前（即，当显式断开连接成功时，我仍然收到“意外断开连接”的信号）

有没有办法区分干净的套接字关闭和客户端上的 kill -9？ （后者仍然表示FIN，所以理论上应该可以检测和区分）

下图的代码（从 here 修改；使用 gcc -lzmq zmq_test.c && ./a.out 编译和运行）

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <zmq.h>

// Read one event off the monitor socket; return value and address
// by reference,if not null,and event number by value. Returns -1
// in case of error.
static int get_monitor_event (void *monitor,int *value,char **address)
{
    // First frame in message contains event number and value
    zmq_msg_t msg;
    zmq_msg_init (&msg);
    if (zmq_msg_recv (&msg,monitor,0) == -1)
        return -1; // Interruped,presumably
    assert (zmq_msg_more (&msg));

    uint8_t *data = (uint8_t *) zmq_msg_data (&msg);
    uint16_t event = *(uint16_t *) (data);
    if (value)
        *value = *(uint32_t *) (data + 2);

    // Second frame in message contains event address
    zmq_msg_init (&msg);
    if (zmq_msg_recv (&msg,presumably
    assert (!zmq_msg_more (&msg));

    if (address) {
        uint8_t *data = (uint8_t *) zmq_msg_data (&msg);
        size_t size = zmq_msg_size (&msg);
        *address = (char *) malloc (size + 1);
        memcpy (*address,data,size);
        *address [size] = 0;
    }
    printf("event: %d\n",event);
    return event;
}

static void close_zero_linger(void *socket)
{
    int linger = 0;
    zmq_setsockopt(socket,ZMQ_LINGER,&linger,sizeof(linger));
    zmq_close(socket);
}

static void bounce(void *client,void *server)
{
    char send_buf[] = "Hello";
    char recv_buf[sizeof(send_buf) / sizeof(send_buf[0])];

    zmq_send(client,send_buf,sizeof(send_buf),0);
    zmq_recv(server,recv_buf,sizeof(recv_buf),0);
    zmq_send(server,0);
    zmq_recv(client,0);
}

int main (void)
{
    void *ctx = zmq_ctx_new ();
    void *client = zmq_socket (ctx,ZMQ_REQ);
    void *server = zmq_socket (ctx,ZMQ_REP);
    int rc = zmq_socket_monitor (client,"tcp://127.0.0.1:9999",0);

    // Monitor all events on client and server sockets
    rc = zmq_socket_monitor (server,"inproc://monitor-server",ZMQ_EVENT_ALL)
    void *server_mon = zmq_socket (ctx,ZMQ_PAIR);
    rc = zmq_connect (server_mon,"inproc://monitor-server");

    // Now do a basic ping test
    rc = zmq_bind (server,"tcp://127.0.0.1:9998");
    rc = zmq_connect (client,"tcp://127.0.0.1:9998");
    bounce (client,server);

//  Close client
    rc = zmq_disconnect(client,"tcp://127.0.0.1:9998");
    printf("disconnect: %d\n",rc);
//    close_zero_linger (client);
    rc = zmq_close(client);
    printf("close: %d\n",rc);
//   sleep(1); // no difference

    // This is the flow of server events
    event = get_monitor_event (server_mon,NULL,NULL);
    assert (event == ZMQ_EVENT_LISTENING);
    event = get_monitor_event (server_mon,NULL);
    assert (event == ZMQ_EVENT_ACCEPTED);
    event = get_monitor_event (server_mon,NULL);
    assert (event == ZMQ_EVENT_HANDSHAKE_SUCCEEDED);
//   sleep(1); // no difference
    event = get_monitor_event (server_mon,NULL);
//    assert (event == ZMQ_EVENT_CLOSED);
//    event = get_monitor_event (server_mon,NULL);
//    assert (event == ZMQ_EVENT_MONITOR_STOPPED);
    assert (event == ZMQ_EVENT_DISCONNECTED); // why??

    // Close down the sockets
    close_zero_linger (server);
    close_zero_linger (server_mon);
    zmq_ctx_term (ctx);

    return 0;
}

解决方法

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