如何解决外部服务器的 C++ 客户端和外部客户端的服务器同时使用 boost::asio 协程
是否可以创建一个客户端和服务器并行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，我们可以在任何可能的方向接收/发送数据。
- Server (PORT A) -> APP(client-> 处理消息并发送到 ->server (PORT B)) -> ClientA
- Server (PORT A) APP(client
- 服务器（端口 A）-> APP（客户端-> 处理消息并发送到到服务器（端口 A）
- ClientA -> APP(server(PORT B)->处理消息并发送给给Client 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，但我正在努力解决。
我尝试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。
解决方法
我有一个场景，我需要既是客户端又是服务器，我们可以在任何可能的方向接收/发送数据。
这对于网络应用程序来说是非常标准的。
聊天服务器似乎是一个很好的例子（因为它可以向所有方向发送/接收）：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：
让我们创建一个服务器，为每个接受的会话生成一个异步会话 联系。每个会话都是一个“反向回声”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，让我们运行 5 个客户端。由于需要外部服务器，我们将让它们连接到我们自己的服务器。
这让我们可以有一个自包含的演示，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),yc);
if (!response.empty())
response.pop_back();
log("Received response ",std::quoted(response));
}
});
}
其中 delay 是随机延迟（500..1500 毫秒）：
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 秒钟，然后退出：
io.run_for(3s);
logger("main")("Bye");
印刷品
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
#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,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,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,yc);
msg = msg.substr(n);
}
});
}
});
// a random client,just for this demo
for (auto client_id = 0; client_id<5; ++client_id) {
spawn(io,log=logger("client #" + std::to_string(client_id))]
(ba::yield_context yc) {
tcp::resolver r(io);
tcp::socket s(io);
async_connect(s,yc);
while (true) {
delay(yc);
ba::streambuf buf;
std::ostream(&buf)
<< "Hello from client #" << client_id << "\n";
async_write(s,yc);
std::string response;
async_read_until(s,yc);
if (!response.empty())
response.pop_back();
log("Received response ",std::quoted(response));
}
});
}
io.run_for(3s);
logger("main")("Bye");
}
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