用c++写出客户端和服务端代码利用udp协议引入txt文档进行机器人一问一答，而不是直接把文档的所有内容打印出来。

以下是基于 UDP 协议的 C++ 客户端和服务端代码实现机器人一问一答，从文本文件中读取问题和答案：

服务端代码：

#include <iostream>
#include <fstream>
#include <string>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>

using namespace std;

#define PORT 8888
#define MAXSIZE 1024

int main()
{
    // 打开文件
    ifstream file("qa.txt");
    if (!file.is_open()) {
        cerr << "Failed to open file." << endl;
        return -1;
    }

    // 读取文件内容
    string line;
    string question;
    string answer;
    while (getline(file, line)) {
        if (line.empty()) {
            continue;
        }
        if (line[0] == '#') {
            if (!question.empty() && !answer.empty()) {
                cout << "Q: " << question << endl;
                cout << "A: " << answer << endl;
                cout << endl;
                question = "";
                answer = "";
            }
            question = line.substr(1);
        } else {
            answer += line;
        }
    }

    // 创建 socket
    int sockfd;
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 设置服务器地址
    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(PORT);
    servaddr.sin_addr.s_addr = INADDR_ANY;

    // 绑定 socket
    if (bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // 接收客户端消息并回复
    char buffer[MAXSIZE];
    struct sockaddr_in clientaddr;
    socklen_t len = sizeof(clientaddr);
    while (true) {
        memset(buffer, 0, sizeof(buffer));
        int n = recvfrom(sockfd, (char *)buffer, MAXSIZE, MSG_WAITALL, (struct sockaddr *)&clientaddr, &len);
        buffer[n] = '\0';
        cout << "Received client message: " << buffer << endl;
        if (strcmp(buffer, "exit") == 0) {
            break;
        }
        string reply = answer.empty() ? "Sorry, I don't know." : answer;
        sendto(sockfd, reply.c_str(), reply.length(), MSG_CONFIRM, (const struct sockaddr *)&clientaddr, len);
    }

    // 关闭 socket
    close(sockfd);
    return 0;
}

客户端代码：

#include <iostream>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>

using namespace std;

#define PORT 8888
#define MAXSIZE 1024

int main()
{
    // 创建 socket
    int sockfd;
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    // 设置服务器地址
    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(PORT);
    servaddr.sin_addr.s_addr = INADDR_ANY;

    // 发送消息给服务器
    char buffer[MAXSIZE];
    struct sockaddr_in serv_addr;
    socklen_t len = sizeof(serv_addr);
    while (true) {
        cout << "Please input your question: ";
        cin.getline(buffer, MAXSIZE);
        sendto(sockfd, buffer, strlen(buffer), MSG_CONFIRM, (const struct sockaddr *)&servaddr, len);
        if (strcmp(buffer, "exit") == 0) {
            break;
        }
        memset(buffer, 0, sizeof(buffer));
        int n = recvfrom(sockfd, (char *)buffer, MAXSIZE, MSG_WAITALL, (struct sockaddr *)&serv_addr, &len);
        buffer[n] = '\0';
        cout << "Answer: " << buffer << endl;
    }

    // 关闭 socket
    close(sockfd);
    return 0;
}

注意，在运行服务端程序之前，需要创建一个名为 “qa.txt” 的文本文件，并按照以下格式填写问题和答案：

# Question 1
Answer 1.

# Question 2
Answer 2.

...

其中，“#” 后面的内容为问题，接下来的内容为答案。每个问题和答案之间需要用空行分隔开。