c++实现文件传输代码

在C++中实现文件传输通常涉及到网络编程，特别是通过socket通信来发送和接收文件。这里是一个简单的例子，展示了如何使用`std::ifstream`读取本地文件，并使用`std::ofstream`写入到另一台远程主机上：

#include <iostream>
#include <fstream>
#include <string>
#include <sys/socket.h> // 对于socket操作
#include <arpa/inet.h>   // 对于inet_addr等网络函数

// 创建套接字并设置为TCP/IP
int create_socket() {
    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        std::cerr << "Error creating socket" << std::endl;
        return -1;
    }
    return sock;
}

// 连接到服务器
bool connect_to_server(int sock, const char* server_ip, int port) {
    struct sockaddr_in server_address;
    bzero(&server_address, sizeof(server_address));
    server_address.sin_family = AF_INET;
    inet_aton(server_ip, &server_address.sin_addr);
    server_address.sin_port = htons(port);

    if (connect(sock, (struct sockaddr*)&server_address, sizeof(server_address)) == -1) {
        perror("Error connecting to server");
        close(sock);
        return false;
    }
    return true;
}

// 发送文件
void send_file(const std::string& filename, int sock) {
    std::ifstream file(filename, std::ios::binary);
    if (!file.is_open()) {
        std::cerr << "Failed to open file " << filename << std::endl;
        return;
    }

    std::string buffer((std::istreambuf_iterator<char>(file)), {});
    file.close();

    std::cout << "Sending file..." << std::endl;
    send(sock, buffer.c_str(), buffer.size(), 0);
}

// 接收文件
void receive_file(int sock, std::string& output_filename) {
    char received_buffer[4096];
    size_t bytes_received;

    std::ofstream output(output_filename, std::ios::binary | std::ios::trunc);
    if (!output.is_open()) {
        std::cerr << "Failed to open output file" << std::endl;
        return;
    }

    while ((bytes_received = recv(sock, received_buffer, sizeof(received_buffer), 0)) > 0) {
        output.write(received_buffer, bytes_received);
    }

    output.close();
    if (bytes_received == 0) {
        std::cerr << "Server closed connection." << std::endl;
    } else if (bytes_received == -1) {
        perror("Error receiving file");
    }
}

int main() {
    int sock = create_socket();
    if (sock < 0) {
        return 1;
    }

    // 设置服务器地址和端口
    char server_ip[] = "your_server_ip";
    int port = your_server_port;

    if (!connect_to_server(sock, server_ip, port)) {
        return 1;
    }

    std::string input_filename = "path_to_your_input_file";
    std::string output_filename = "output_file_name";

    send_file(input_filename, sock); // 发送文件
    receive_file(sock, output_filename); // 接收文件

    close(sock);
    return 0;
}

注意这只是一个基础示例，实际应用中还需要处理错误、异常以及连接关闭等情况。此外，为了安全性和效率，最好使用SSL/TLS进行加密通信。