C++ ZMQ

笔者最近在使用ZMQ来实现数据之间的通讯，在使用到zmq_socket这个函数时有一个option是SNDHWM，官方API上对其的行为解释是当达到高水位，也就是用SNDHWM设定的最高点后，会丢弃数据，我想查看一下达到高水位后zmq真正的行为是什么样的，于是进行了实验，结果如下。

一些程序
ROUTER端：

int sndhwm=600;
    size_t sndhwm_size = sizeof(sndhwm);
    int rc = zmq_setsockopt(du, ZMQ_SNDHWM, &sndhwm, sndhwm_size);
    assert(rc == 0);

发送行为：

for(int i = 0; i < 1000; i++) {
        msg1 = zmq_send(du, adaq_address, size, ZMQ_SNDMORE);
        msg2 = zmq_send(du, "", sizeof(""), ZMQ_SNDMORE);
        msg3 = zmq_send(du, buf, 4096, 0);
        cout << msg2 << endl;
        cout << msg3 << endl;
        cout << "buffer is " << buf << endl;
        cout << "loop number is " << loop < 
DEALER端;
 接收行为
 
while(1) {
        int msg = zmq_recv(socket, buffer, sizeof(buffer), 0);
        int msg2 = zmq_recv(socket, buf1, sizeof(buffer), 0);
        
        int r1 = zmq_getsockopt(socket, ZMQ_RCVMORE, &more, &more_size);
        loop++;
        std::cout << "    " << std::endl;
        std::cout << "loop is " << loop << std::endl;
        std::cout << "recv return value 1 is " << msg << std::endl;
        std::cout << "recv return value 2 is " << msg2 << std::endl;
        std::cout << "buffer is " << buffer << std::endl;
        std::cout << "buf1 is " << buf1 << std::endl;
        std::cout << "    " << std::endl;
    }
 
结果如下：
 ROUTER端的send函数在1000次发送显示正常，但DEALER端在sndhwm的值设为600后，只能轮询接收数据600次。结果如下：
 
ROUTER端
 
1
4096
buffer is 0x01
loop number is 998
1
4096
buffer is 0x01
loop number is 999
 
DEALER端：
 
loop is 600
recv return value 1 is 1
recv return value 2 is 4096
buffer is
buf1 is 0x01

 
DEALER端因用while一直等待来自router的数据，因此当loop为600的时候不在收到来自ROUTER的数据，即ROUTER丢弃了600次send之后的数据。
 
以上、