Asynchronous client/server in C++

// Asynchronous client-to-server (DEALER to ROUTER)
//
// While this example runs in a single process, that is to make
// it easier to start and stop the example. Each task has its own
// context and conceptually acts as a separate process.

#include <vector>
#include <thread>
#include <memory>
#include <functional>

#include <zmq.hpp>
#include <zhelpers.hpp>

// This is our client task class.
// It connects to the server, and then sends a request once per second
// It collects responses as they arrive, and it prints them out. We will
// run several client tasks in parallel, each with a different random ID.
// Attention! -- this random work well only on linux.

class client_task {
public:
client_task()
: ctx_(1),
client_socket_(ctx_, ZMQ_DEALER)
{}

void start() {
// generate random identity
char identity[10] = {};
sprintf(identity, "%04X-%04X", within(0x10000), within(0x10000));
printf("%s\n", identity);
client_socket_.setsockopt(ZMQ_IDENTITY, identity, strlen(identity));
client_socket_.connect("tcp://localhost:5570");

zmq::pollitem_t items[] = client_socket_, 0, ZMQ_POLLIN, 0;
int request_nbr = 0;
try {
while (true) {
for (int i = 0; i < 100; ++i) {
// 10 milliseconds
zmq::poll(items, 1, 10);
if (items[0].revents & ZMQ_POLLIN) {
printf("\n%s ", identity);
s_dump(client_socket_);
}
}
char request_string[16] = {};
sprintf(request_string, "request #%d", ++request_nbr);
client_socket_.send(request_string, strlen(request_string));
}
}
catch (std::exception &e) {}
}

private:
zmq::context_t ctx_;
zmq::socket_t client_socket_;
};

// Each worker task works on one request at a time and sends a random number
// of replies back, with random delays between replies:

class server_worker {
public:
server_worker(zmq::context_t &ctx, int sock_type)
: ctx_(ctx),
worker_(ctx_, sock_type)
{}

void work() {
worker_.connect("inproc://backend");

try {
while (true) {
zmq::message_t identity;
zmq::message_t msg;
zmq::message_t copied_id;
zmq::message_t copied_msg;
worker_.recv(&identity);
worker_.recv(&msg);

int replies = within(5);
for (int reply = 0; reply < replies; ++reply) {
s_sleep(within(1000) + 1);
copied_id.copy(&identity);
copied_msg.copy(&msg);
worker_.send(copied_id, ZMQ_SNDMORE);
worker_.send(copied_msg);
}
}
}
catch (std::exception &e) {}
}

private:
zmq::context_t &ctx_;
zmq::socket_t worker_;
};

// This is our server task.
// It uses the multithreaded server model to deal requests out to a pool
// of workers and route replies back to clients. One worker can handle
// one request at a time but one client can talk to multiple workers at
// once.

class server_task {
public:
server_task()
: ctx_(1),
frontend_(ctx_, ZMQ_ROUTER),
backend_(ctx_, ZMQ_DEALER)
{}

enum { kMaxThread = 5 };

void run() {
frontend_.bind("tcp://*:5570");
backend_.bind("inproc://backend");

std::vector<server_worker *> worker;
std::vector<std::thread *> worker_thread;
for (int i = 0; i < kMaxThread; ++i) {
worker.push_back(new server_worker(ctx_, ZMQ_DEALER));

worker_thread.push_back(new std::thread(std::bind(&server_worker::work, worker)));
worker_thread->detach();
}

try {
zmq::proxy(frontend_, backend_, nullptr);
}
catch (std::exception &e) {}

for (int i = 0; i < kMaxThread; ++i) {
delete worker;
delete worker_thread;
}
}

private:
zmq::context_t ctx_;
zmq::socket_t frontend_;
zmq::socket_t backend_;
};

// The main thread simply starts several clients and a server, and then
// waits for the server to finish.

int main (void)
{
client_task ct1;
client_task ct2;
client_task ct3;
server_task st;

std::thread t1(std::bind(&client_task::start, &ct1));
std::thread t2(std::bind(&client_task::start, &ct2));
std::thread t3(std::bind(&client_task::start, &ct3));
std::thread t4(std::bind(&server_task[[span style="color:#666666"]]::run, [[span style="color:#666666"]]&st));

t1.detach();
t2.detach();
t3.detach();
t4.detach();

getchar();
[[span style="color:#008000"]]return [[span style="color:#666666"]]0;
}