客户端和服务端通信----buffer

buffer

在网络编程中，操作系统底层 API(如 send()、recv())要求传入：

• 一个 内存地址（指针）
• 一个 字节数(size)
  

但 C++ 中有多种数据类型（std::string、std::vector<char>、C 数组等），Asio 需要一个统一接口来表示“一块连续内存”。于是，Asio 引入了 Buffer 模型 —— 不是具体类，而是一套概念（Concept）和辅助函数。

类型	用途	函数
ConstBufferSequence	只读（用于发送数据）	write, send
MutableBufferSequence	可写（用于接收数据）	read，receive

Asio 提供重载的 asio::buffer() 函数，将常见容器转换为 buffer。

同步读写的客户端和服务端实例

//客户端
#include <iostream>
#include <boost/asio.hpp>
#include <string>
#include <cstring>namespace asio = boost::asio;
using tcp = asio::ip::tcp;const int MAX_LENGTH = 1024;
int main()
{std::string serverIP_ = "127.0.0.1";const unsigned short port = 9999;try{// 1. 创建上下文服务asio::io_context ioc;// 2. 构造endpointauto serverIpAddress_ = asio::ip::make_address(serverIP_);tcp::endpoint serverEndpoint_ = tcp::endpoint(serverIpAddress_, port);// 3. 连接到服务端tcp::socket sock_ = tcp::socket(ioc);boost::system::error_code ec;sock_.connect(serverEndpoint_, ec);if (ec){std::cout << "client connect fail: " << ec.message() << std::endl;return -1;}// 4.发送消息std::cout << "Enter message" << std::endl;char buffer[MAX_LENGTH];std::cin.getline(buffer, MAX_LENGTH);asio::write(sock_, asio::buffer(buffer, strlen(buffer)));// 5.接收消息std::string reply;asio::streambuf sb;size_t replyLength = asio::read_until(sock_, sb, '\n', ec);if (ec && ec != asio::error::eof){std::cout << "read error" << ec.message() << std::endl;}reply = std::string(std::istreambuf_iterator<char>(&sb), {});std::cout << "recvive message is: " << reply << std::endl;}catch (const std::exception& error){std::cout << error.what() << std::endl;return -1;}return 0;
}

//服务端
#include <iostream>
#include <boost/asio.hpp>
#include <cstring>namespace asio = boost::asio;
using tcp = asio::ip::tcp;const unsigned short PORT = 9999;
const int MAX_LENGTH = 1024;
int main()
{try{// 1. 创建上下文asio::io_context ioc;// 2.创建socket open + bind + listenboost::system::error_code ec;tcp::endpoint serverEndpoint = tcp::endpoint(tcp::v4(), PORT);tcp::acceptor acceptor(ioc, serverEndpoint);// 3.accepttcp::socket client = acceptor.accept();// 4.接收数据std::string reply;asio::streambuf streamBuf;size_t replyLength = asio::read_until(client, streamBuf, '\n', ec);if (ec && ec != asio::error::eof){std::cout << "read error" << ec.message() << std::endl;return -1;}reply = std::string(std::istreambuf_iterator<char>(&streamBuf), {});std::cout << "received message : " << reply << std::endl;// 5.发送数据std::cout << "Enter Message" << std::endl;char buf[MAX_LENGTH];std::cin.getline(buf, MAX_LENGTH);asio::write(client, asio::buffer(buf, strlen(buf)),ec);if (ec){std::cout << "send error" << ec.message() << std::endl;return -1;}}catch (const std::exception& error){std::cout << error.what() << std::endl;return -1;}return 0;
}