以下ASIO聊天室客户端例子:
#include “chat_message.h”
//client.cpp
#include <boost/asio.hpp>
#include <deque>
#include <iostream>
#include <thread>
#include <cstdlib>
using boost::asio::ip::tcp;
using chat_message_queue = std::deque<chat_message>;
class chat_client {
public:
chat_client(boost::asio::io_service &io_service,
tcp::resolver::iterator endpoint_iterator)
: io_service_(io_service), socket_(io_service) {
do_connect(endpoint_iterator);
}
void write(const chat_message &msg) {
io_service_.post([this, msg]() {
bool write_in_progress = !write_msgs_.empty();
write_msgs_.push_back(msg);
if (!write_in_progress) {
do_write();
}
});
}
void close() {
io_service_.post([this]() { socket_.close(); });
}
private:
void do_connect(tcp::resolver::iterator endpoint_iterator) {
boost::asio::async_connect(
socket_, endpoint_iterator,
[this](boost::system::error_code ec, tcp::resolver::iterator) {
if (!ec) {
do_read_header();
}
});
}
void do_read_header() {
boost::asio::async_read(
socket_,
boost::asio::buffer(read_msg_.data(), chat_message::header_length),
[this](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec && read_msg_.decode_header()) {
do_read_body();
} else {
socket_.close();
}
});
}
void do_read_body() {
boost::asio::async_read(
socket_, boost::asio::buffer(read_msg_.body(), read_msg_.body_length()),
[this](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec) {
std::cout.write(read_msg_.body(), read_msg_.body_length());
std::cout << "\n";
do_read_header();
} else {
socket_.close();
}
});
}
void do_write() {
boost::asio::async_write(
socket_, boost::asio::buffer(write_msgs_.front().data(),
write_msgs_.front().length()),
[this](boost::system::error_code ec, std::size_t /*length*/) {
if (!ec) {
write_msgs_.pop_front();
if (!write_msgs_.empty()) {
do_write();
}
} else {
socket_.close();
}
});
}
private:
boost::asio::io_service &io_service_;
tcp::socket socket_;
chat_message read_msg_;
chat_message_queue write_msgs_;
};
int main(int argc, char *argv[]) {
try {
if (argc != 3) {
std::cerr << "Usage: chat_client <host> <port>\n";
return 1;
}
boost::asio::io_service io_service;
tcp::resolver resolver(io_service);
auto endpoint_iterator = resolver.resolve({argv[1], argv[2]});
chat_client c(io_service, endpoint_iterator);
std::thread t([&io_service]() { io_service.run(); });
char line[chat_message::max_body_length + 1];
// ctrl-d
while (std::cin.getline(line, chat_message::max_body_length + 1)) {
chat_message msg;
msg.body_length(std::strlen(line));
std::memcpy(msg.body(), line, msg.body_length());
msg.encode_header();
c.write(msg);
}
c.close();
t.join();
} catch (std::exception &e) {
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}
客户端的io_service.run要在子线程中跑因为会阻塞
void write(const chat_message &msg) {
io_service_.post(this, msg {
对msg进行了值的拷贝并用io_service_.post注册了一个事件在io_service的控制中最终在run下执行
在外部调度用c.write注册事件放到t线程中最终在t线程下调用run执行,service能调度在哪个线程下运行防止多个线程并行处理事件出现问题,当前只有t线程
真正调用do_read_header是在run线程下执行的所以可以直接用socket_.close(),同个io_service_跑run下不会有抢资源,死锁之类的问题
用c.close()清空注册事件再t.join才能结束子线程
ctrl+d正常退出客户端,ctrl+c中断信号