c++实现凯撒密码算法及UDP网络传输接收显示

凯撒密码是一种简单的加密技术，通过将明文字符按照固定的偏移量替换来实现加密。在C++中，你可以这样实现：

#include <iostream>
#include <string>

// 函数用于加密
std::string caesar_cipher_encrypt(const std::string& plaintext, int shift) {
    std::string ciphertext;
    for (char c : plaintext) {
        if (isalpha(c)) { // 检查是否为字母
            char encrypted_c = static_cast<char>((c + shift - 'A') % 26 + 'A'); // 加密处理
            ciphertext += encrypted_c;
        } else {
            ciphertext += c; // 非字母字符不变
        }
    }
    return ciphertext;
}

// 函数用于解密
std::string caesar_cipher_decrypt(const std::string& ciphertext, int shift) {
    return caesar_cipher_encrypt(ciphertext, -shift);
}

int main() {
    std::string message = "Hello, World!";
    int shift = 3; // 密钥

    std::cout << "Original Message: " << message << std::endl;
    std::string encrypted = caesar_cipher_encrypt(message, shift);
    std::cout << "Encrypted Message: " << encrypted << std::endl;

    // 解密示例
    std::string decrypted = caesar_cipher_decrypt(encrypted, shift);
    std::cout << "Decrypted Message: " << decrypted << std::endl;

    return 0;
}

至于UDP网络传输和接收到的数据显示，首先你需要创建一个UDP套接字并监听数据。这里是一个基本的例子：

#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

void send_data(char* data, const char* ip, int port) {
    // 创建socket
    int sock = socket(AF_INET, SOCK_DGRAM, 0);

    struct sockaddr_in server_address;
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(port);
    inet_pton(AF_INET, ip.c_str(), &server_address.sin_addr);

    sendto(sock, data, strlen(data), 0, (struct sockaddr*)&server_address, sizeof(server_address));
    close(sock);
}

void receive_and_display() {
    int sock = socket(AF_INET, SOCK_DGRAM, 0);
    struct sockaddr_in client_address;
    socklen_t addr_size = sizeof(client_address);

    char buffer[1024];
    while (true) {
        ssize_t bytes_received = recvfrom(sock, buffer, sizeof(buffer), 0, (struct sockaddr*)&client_address, &addr_size);
        if (bytes_received > 0) {
            std::cout << "Received: " << buffer << " from " << inet_ntoa(client_address.sin_addr) << ":" << ntohs(client_address.sin_port) << std::endl;
        } else {
            break;
        }
    }
    close(sock);
}

int main() {
    char message[] = "This is a UDP message.";
    std::string encrypted = caesar_cipher_encrypt(message, shift); // 将上面的message替换成加密后的字符串

    send_data(encrypted.c_str(), "your_server_ip", your_server_port); // 发送到服务器

    receive_and_display(); // 接收并显示接收到的数据（注意这需要服务器端配合）

    return 0;
}