外部服务器的 C++ 客户端和外部客户端的服务器同时使用 boost::asio 协程

Question

是否可以并行创建一个包含客户端和服务器运行并在它们之间进行通信的单线程进程？

我有一个场景，我需要既是客户端又是服务器，我们可以receive/send任何可能方向的数据。

Server (PORT A) -> APP(client-> process message and send to ->server (PORT B)) -> ClientA
Server (PORT A) <- APP(client<- process message and send to <-server (PORT B)) <- ClientA
Server (PORT A) -> APP(client-> process message and send to to Server (PORT A)
ClientA -> APP(server(PORT B)-> 处理消息并发送到 到客户端 A

我一直在尝试使用示例中提供的 boost::asio 协程修改示例，并在 io_context 或单独的 io_context 中添加客户端，但我正在努力有了它。

我试过将客户端和服务器放在不同的线程中，但我也遇到了并发问题...任何想法或片段将不胜感激。

Answer 1

I have an scenario where I need to be both client and server and we can receive/send data in any possible direction.

这是网络应用程序的标准配置。

聊天服务器似乎是一个很好的例子（因为它在所有方向上都 send/receive）：https://www.boost.org/doc/libs/1_75_0/doc/html/boost_asio/examples/cpp11_examples.html#boost_asio.examples.cpp11_examples.chat

现在，作为也启动传出连接的服务器的准系统示例：

Live On Wandbox

让我们创建一个服务器，为每个接受的请求生成一个异步会话联系。每个会话都是一个“反向回显”服务。

// echo server, multi-client
spawn(io, [&io](ba::yield_context yc) {
    tcp::acceptor acc(io, {{}, 6868});
    acc.set_option(tcp::acceptor::reuse_address(true));

    while (true) {
        tcp::socket s(io);
        acc.async_accept(s, yc);
        spawn(yc, [s = std::move(s)]
            (ba::yield_context yc) mutable {
            log("Connection from ", s.remote_endpoint());
            std::string msg;
            while (auto n = async_read_until(s, ba::dynamic_buffer(msg), "\n", yc)) {
                std::string_view vw(msg.data(), n);
                vw.remove_suffix(1); // leave '\n'
                log("Responding to ", std::quoted(vw));

                std::reverse(msg.data(), msg.data() + vw.size());

                async_write(s, ba::buffer(msg, n), yc);
                msg = msg.substr(n);
            }
        });
    }
});

同时，我们运行 5 个客户。如果没有外部服务器，我们会让他们连接到我们自己的服务器。

这允许我们有一个独立的演示，并将证明单线程不会导致任何阻塞。

// a random client, let's make it connect to our own server, just for this demo
for (auto client_id = 0; client_id<5; ++client_id) {
    spawn(io,
        [&io, delay, client_id, log=logger("client #" + std::to_string(client_id))]
        (ba::yield_context yc) {
            tcp::resolver r(io);
            tcp::socket s(io);
            async_connect(s, r.async_resolve("127.0.0.1", "6868", yc), yc);

            while (true) {
                delay(yc);
                ba::streambuf buf;
                std::ostream(&buf)
                    << "Hello from client #" << client_id << "\n";

                async_write(s, buf, yc);

                std::string response;
                async_read_until(s, ba::dynamic_buffer(response), "\n", yc);
                if (!response.empty())
                    response.pop_back();

                log("Received response ", std::quoted(response));
            }
        });
}

其中delay是随机延迟（500..1500ms）：

auto delay = [&io](ba::yield_context yc) {
    ba::steady_timer(io, 500ms + (prng() % 1000) * 1ms)
        .async_wait(yc);
};

我们运行整个程序3秒，然后退出：

io.run_for(3s);
logger("main")("Bye");

版画

at     0ms  session #0  Connection from 127.0.0.1:51024
at     1ms  session #1  Connection from 127.0.0.1:51026
at     1ms  session #2  Connection from 127.0.0.1:51028
at     1ms  session #3  Connection from 127.0.0.1:51030
at     1ms  session #4  Connection from 127.0.0.1:51032
at   831ms  session #3  Responding to "Hello from client #3"
at   831ms  client #3   Received response "3# tneilc morf olleH"
at  1148ms  session #4  Responding to "Hello from client #4"
at  1148ms  client #4   Received response "4# tneilc morf olleH"
at  1196ms  session #1  Responding to "Hello from client #1"
at  1196ms  client #1   Received response "1# tneilc morf olleH"
at  1327ms  session #0  Responding to "Hello from client #0"
at  1327ms  client #0   Received response "0# tneilc morf olleH"
at  1401ms  session #2  Responding to "Hello from client #2"
at  1401ms  client #2   Received response "2# tneilc morf olleH"
at  1446ms  session #3  Responding to "Hello from client #3"
at  1446ms  client #3   Received response "3# tneilc morf olleH"
at  1836ms  session #4  Responding to "Hello from client #4"
at  1836ms  client #4   Received response "4# tneilc morf olleH"
at  2163ms  session #0  Responding to "Hello from client #0"
at  2163ms  client #0   Received response "0# tneilc morf olleH"
at  2382ms  session #2  Responding to "Hello from client #2"
at  2383ms  client #2   Received response "2# tneilc morf olleH"
at  2426ms  session #3  Responding to "Hello from client #3"
at  2426ms  client #3   Received response "3# tneilc morf olleH"
at  2444ms  session #4  Responding to "Hello from client #4"
at  2444ms  client #4   Received response "4# tneilc morf olleH"
at  2579ms  session #1  Responding to "Hello from client #1"
at  2580ms  client #1   Received response "1# tneilc morf olleH"
at  3002ms  main    Bye

完整列表

Live On Wandbox

#include <boost/asio/detail/handler_alloc_helpers.hpp>
#include <boost/system/system_error.hpp>
#define BOOST_BIND_NO_PLACEHOLDERS
#include <boost/asio.hpp>
#include <boost/asio/spawn.hpp>
#include <iostream>
#include <iomanip>
#include <thread>
#include <chrono>
#include <random>

namespace ba = boost::asio;
using ba::ip::tcp;

using namespace std::literals;

static auto const now = &std::chrono::steady_clock::now;
static auto const start = now();

auto logger(std::string name) {
    return [name](auto const&... args) {
        ((std::cout << "at" << std::setw(6) << (now() - start)/1ms << "ms\t"
                    << name << "\t") 
            << ... << args) << std::endl;
    };
}

int main() {
    ba::io_context io;

    static std::mt19937 prng { std::random_device{}() };

    // insert random async delays
    auto delay = [&io](auto yc) {
        ba::steady_timer(io, 500ms + (prng() % 1000) * 1ms)
            .async_wait(yc);
    };

    // echo server, multi-client
    spawn(io, [&io, log=logger("accept")](ba::yield_context yc) {
        tcp::acceptor acc(io, {{}, 6868});
        acc.set_option(tcp::acceptor::reuse_address(true));

        auto num_clients = 0;
        while (true) {
            tcp::socket s(io);
            acc.async_accept(s, yc);
            spawn(yc, [s = std::move(s), log=logger("session #" + std::to_string(num_clients++))]
                (ba::yield_context yc) mutable {
                log("Connection from ", s.remote_endpoint());
                std::string msg;
                while (auto n = async_read_until(s, ba::dynamic_buffer(msg), "\n", yc)) {
                    std::string_view vw(msg.data(), n);
                    vw.remove_suffix(1); // leave '\n'
                    log("Responding to ", std::quoted(vw));

                    std::reverse(msg.data(), msg.data() + vw.size());

                    async_write(s, ba::buffer(msg, n), yc);
                    msg = msg.substr(n);
                }
            });
        }
    });

    // a random client, let's make it connect to our own server, just for this demo
    for (auto client_id = 0; client_id<5; ++client_id) {
        spawn(io,
            [&io, delay, client_id, log=logger("client #" + std::to_string(client_id))]
            (ba::yield_context yc) {
                tcp::resolver r(io);
                tcp::socket s(io);
                async_connect(s, r.async_resolve("127.0.0.1", "6868", yc), yc);

                while (true) {
                    delay(yc);
                    ba::streambuf buf;
                    std::ostream(&buf)
                        << "Hello from client #" << client_id << "\n";

                    async_write(s, buf, yc);

                    std::string response;
                    async_read_until(s, ba::dynamic_buffer(response), "\n", yc);
                    if (!response.empty())
                        response.pop_back();

                    log("Received response ", std::quoted(response));
                }
            });
    }

    io.run_for(3s);
    logger("main")("Bye");
}

外部服务器的 C++ 客户端和外部客户端的服务器同时使用 boost::asio 协程

C++ Client for external server & Server for external clients simultaneously with boost::asio coroutine

c++

boost

boost-asio

coroutine

c++-coroutine

完整列表