ZMQ_SNDBUF&&ZMQ_RCVBUF on ZMQ_PUB&&ZMQ_SUB no effect - zeromq

Question

Issue description
I used ZMQ_SNDBUF && ZMQ_RCVBUF on ZMQ_PUB&&ZMQ_SUB no effect.
But I executed the following command and it worked.
sudo sysctl -w net.core.wmem_default=5000
Before modifying net.core.wmem_default
The receiving end continues to receive 3757 frames and then refresh.
After modifying net.core.wmem_default
The receiving end continues to receive 22 frames and then refreshes.
Environment
libzmq version (commit hash if unreleased):
4.3.3
OS:
ubuntu18.04
Is that why?
Code
sender
//
// Created by kongshui on 22-8-23.
//
#include <unistd.h>
#include <iostream>
#include <zmq.hpp>
void main()
{
const int first_count = 10000000;
int hwm = 5;
int time = 10;
auto con = zmq_ctx_new();
// Set up bind socket
void *pub_socket = zmq_socket(con, ZMQ_PUB);
zmq_setsockopt(pub_socket, ZMQ_SNDTIMEO, &time, sizeof(time));
zmq_setsockopt(pub_socket, ZMQ_RCVTIMEO, &time, sizeof(time));
zmq_setsockopt(pub_socket, ZMQ_SNDHWM, &hwm, sizeof(hwm));
zmq_setsockopt(pub_socket, ZMQ_RCVHWM, &hwm, sizeof(hwm));
zmq_bind(pub_socket, "ipc:///tmp/qos_out");
int buf_size = 5000;
auto rrr = zmq_setsockopt(pub_socket, ZMQ_SNDBUF, &buf_size, sizeof(buf_size));
printf("rrr: %d", rrr);
hwm = 10;
size_t hwm_size = sizeof(hwm);
rrr = zmq_getsockopt(pub_socket, ZMQ_SNDBUF, &hwm, &hwm_size);
printf("rrr: %d, size: %d\n", rrr, hwm);
sleep(3);
// Send messages
int send_count = 0;
int recv_count = 0;
std::string msg;
while (send_count < first_count)
{
msg = std::to_string(send_count);
int res = zmq_send(pub_socket, msg.c_str(), msg.length(), ZMQ_DONTWAIT);
printf("res:%d, msg:%s", res, msg.c_str());
if (msg.length() == res)
++send_count;
else
break;
usleep(1000);
}
// Clean up
zmq_close(pub_socket);
}
receiver
//
// Created by kongshui on 22-8-23.
//
#include <unistd.h>
#include <iostream>
#include <zmq.hpp>
void main()
{
const int first_count = 15;
int hwm = 5;
int time = 10;
auto con = zmq_ctx_new();
hwm = 10;
// Set up connect socket
void *sub_socket = zmq_socket(con, ZMQ_SUB);
zmq_setsockopt(sub_socket, ZMQ_SNDTIMEO, &time, sizeof(time));
zmq_setsockopt(sub_socket, ZMQ_RCVTIMEO, &time, sizeof(time));
zmq_setsockopt(sub_socket, ZMQ_SNDHWM, &hwm, sizeof(hwm));
zmq_setsockopt(sub_socket, ZMQ_RCVHWM, &hwm, sizeof(hwm));
int buf_size = 5000;
std::string topic = "www";
auto rrr = zmq_setsockopt(sub_socket, ZMQ_RCVBUF, &buf_size, sizeof(buf_size));
printf("rrr: %d", rrr);
hwm = 10;
size_t hwm_size = sizeof(hwm);
rrr = zmq_getsockopt(sub_socket, ZMQ_RCVBUF, &hwm, &hwm_size);
printf("rrr: %d, size: %d\n", rrr, hwm);
zmq_connect(sub_socket, "ipc:///tmp/qos_out");
// zmq_setsockopt(sub_socket, ZMQ_SUBSCRIBE, topic.c_str(), topic.size());
zmq_setsockopt(sub_socket, ZMQ_SUBSCRIBE, nullptr, 0);
sleep(3);
// Send messages
int send_count = 0;
int recv_count = 0;
std::string msg;
char res[1024] = {0};
while (zmq_recv(sub_socket, res, 1021, ZMQ_DONTWAIT) > 0)
{
++recv_count;
printf("res:%s", res);
printf("first_count: %d, recv_count: %d\n", first_count, recv_count);
memset(res, 0, sizeof(res));
}
while (1)
{
if (zmq_recv(sub_socket, res, 1021, ZMQ_DONTWAIT) > 0)
{
++recv_count;
printf("res:%s", res);
memset(res, 0, sizeof(res));
printf("first_count: %d, recv_count: %d\n", first_count, recv_count);
sleep(1);
}
}
// Clean up
zmq_close(sub_socket);
}