c++ 本地http服务与客户端实现文件传输代码

这里给出一个基于 Boost.Asio 库的 C++ 实现的简单 HTTP 服务器和客户端，可以实现文件传输的功能。

HTTP 服务器代码：

#include <iostream>
#include <fstream>
#include <boost/asio.hpp>

using namespace boost::asio;
using namespace boost::asio::ip;

const std::string SERVER_ADDR = "127.0.0.1";
const int SERVER_PORT = 8080;
const std::string FILE_PATH = "test.txt";

void handle_request(tcp::socket& socket) {
  boost::array<char, 8192> buf;
  boost::system::error_code error;
  size_t len = socket.read_some(buffer(buf), error);
  if (error == boost::asio::error::eof) {
    return;
  } else if (error) {
    throw boost::system::system_error(error);
  }

  std::string request(buf.data(), len);
  std::string response;

  // parse request and prepare response
  std::stringstream ss(request);
  std::string method, path, version;
  ss >> method >> path >> version;
  std::cout << method << " " << path << " " << version << std::endl;

  std::ifstream file(FILE_PATH, std::ios::binary);
  if (file) {
    file.seekg(0, std::ios::end);
    size_t file_size = file.tellg();
    file.seekg(0, std::ios::beg);

    response = "HTTP/1.1 200 OK\r\n";
    response += "Content-Type: application/octet-stream\r\n";
    response += "Content-Length: " + std::to_string(file_size) + "\r\n";
    response += "\r\n";

    // send response header
    write(socket, buffer(response), error);
    if (error) {
      throw boost::system::system_error(error);
    }

    // send file content
    char file_buf[8192];
    while (file.read(file_buf, sizeof(file_buf)).gcount() > 0) {
      write(socket, buffer(file_buf, file.gcount()), error);
      if (error) {
        throw boost::system::system_error(error);
      }
    }
  } else {
    response = "HTTP/1.1 404 Not Found\r\n";
    response += "\r\n";
    write(socket, buffer(response), error);
    if (error) {
      throw boost::system::system_error(error);
    }
  }
}

int main() {
  io_service service;
  tcp::endpoint ep(address::from_string(SERVER_ADDR), SERVER_PORT);
  tcp::acceptor acceptor(service, ep);

  while (true) {
    tcp::socket socket(service);
    acceptor.accept(socket);
    std::thread t([&socket]() { handle_request(socket); });
    t.detach();
  }
}

HTTP 客户端代码：

#include <iostream>
#include <fstream>
#include <boost/asio.hpp>

using namespace boost::asio;
using namespace boost::asio::ip;

const std::string SERVER_ADDR = "127.0.0.1";
const int SERVER_PORT = 8080;
const std::string FILE_PATH = "test_download.txt";

void download_file(tcp::socket& socket) {
  std::ofstream file(FILE_PATH, std::ios::binary);
  if (!file) {
    throw std::runtime_error("Failed to open file: " + FILE_PATH);
  }

  // send HTTP request
  std::string request = "GET / HTTP/1.1\r\n";
  request += "Host: " + SERVER_ADDR + ":" + std::to_string(SERVER_PORT) + "\r\n";
  request += "Connection: close\r\n";
  request += "\r\n";
  write(socket, buffer(request));

  // read HTTP response
  boost::array<char, 8192> buf;
  boost::system::error_code error;
  size_t len = read_until(socket, buffer(buf), "\r\n\r\n", error);
  if (error) {
    throw boost::system::system_error(error);
  }

  std::string response(buf.data(), len);
  std::cout << response << std::endl;

  // parse response header
  size_t pos = response.find("Content-Length: ");
  if (pos == std::string::npos) {
    throw std::runtime_error("Invalid response header format: " + response);
  }
  size_t file_size = std::stoull(response.substr(pos + 16));

  // read file content
  size_t total_read = 0;
  while (total_read < file_size) {
    size_t read_size = std::min<size_t>(file_size - total_read, sizeof(buf));
    len = read(socket, buffer(buf, read_size), error);
    if (error) {
      throw boost::system::system_error(error);
    }
    file.write(buf.data(), len);
    total_read += len;
  }

  std::cout << "File download finished." << std::endl;
}

int main() {
  io_service service;
  tcp::endpoint ep(address::from_string(SERVER_ADDR), SERVER_PORT);
  tcp::socket socket(service);
  socket.connect(ep);

  download_file(socket);

  socket.close();
}

这里只是一个简单的示例，没有考虑安全性和可靠性等问题，仅供参考。