网络编程

完成下面任务（29分）
1 在 Ubuntu 或 openEuler 中完成任务（推荐openEuler）
2 参考《head first C》实现knock knock服务器，提交代码knock.c，编译运行过程（13分）
3 使用多线程实现knock knock服务器,提交代码knockmt.c,编译运行过程,至少两个客户端测试，服务器运行结果中要打印线程id（13分）
4 提交git log结果（3分）

实现knock knock服务器

代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h> 包含inet_ntoa函数所需头文件

#define PORT 3490
#define BACKLOG 10

void error(const char *msg) {
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[]) {
    int sockfd, new_fd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t sin_size;
    char buffer[256];

    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        error("Error creating socket");
    }

    // 初始化服务器地址结构体
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    server_addr.sin_addr.s_addr = INADDR_ANY;
    memset(server_addr.sin_zero, '\0', sizeof(server_addr.sin_zero));

    // 绑定套接字到指定地址和端口
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        error("Error binding");
    }

    // 监听端口，设置最大等待连接数
    if (listen(sockfd, BACKLOG) == -1) {
        error("Error listening");
    }

    printf("Server is waiting for connections...\n");

    while (1) {
        sin_size = sizeof(client_addr);
        // 接受客户端连接
        new_fd = accept(sockfd, (struct sockaddr *)&client_addr, &sin_size);
        if (new_fd == -1) {
            error("Error accepting connection");
        }

        char *client_ip = inet_ntoa(client_addr.sin_addr);
        printf("Got connection from %s\n", client_ip);

        // 发送初始消息给客户端
        strcpy(buffer, "Knock! Knock!\n");
        write(new_fd, buffer, strlen(buffer));

        // 接收客户端回复
        memset(buffer, 0, sizeof(buffer));
        read(new_fd, buffer, sizeof(buffer) - 1);
        printf("Client said: %s", buffer);

        // 根据客户端回复发送不同响应
        if (strcmp(buffer, "Who's there?\n") == 0) {
            strcpy(buffer, "Oscar.\n");
            write(new_fd, buffer, strlen(buffer));
            // 再次接收客户端回复
            memset(buffer, 0, sizeof(buffer));
            read(new_fd, buffer, sizeof(buffer) - 1);
            printf("Client said: %s", buffer);
            if (strcmp(buffer, "Oscar who?\n") == 0) {
                strcpy(buffer, "Oscar silly question, you get a silly answer.\n");
                write(new_fd, buffer, strlen(buffer));
            } else {
                strcpy(buffer, "I was expecting 'Oscar who?'.\n");
                write(new_fd, buffer, strlen(buffer));
            }
        } else {
            strcpy(buffer, "I was expecting 'Who's there?'.\n");
            write(new_fd, buffer, strlen(buffer));
        }
        close(new_fd);
    }
    close(sockfd);
    return 0;
}

此时服务器开始运行并监听在指定的端口（代码中定义的PORT为3490），终端显示Server is waiting for connections...表示服务器正在等待连接。打开另一个终端窗口，输入telnet localhost 3490来连接服务器：

服务器发送的初始消息Knock! Knock!，表示连接成功。

多线程实现knock knock服务器

代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>

#define PORT 3490
#define BACKLOG 10

// 线程处理函数的参数结构体
typedef struct {
    int client_fd;
} ThreadArgs;

// 错误处理函数
void error(const char *msg) {
    perror(msg);
    exit(1);
}

// 线程处理函数，用于和单个客户端交互
void *handle_client(void *arg) {
    ThreadArgs *args = (ThreadArgs *)arg;
    int client_fd = args->client_fd;
    char buffer[256];
    pthread_t tid = pthread_self();  // 获取当前线程ID

    // 发送初始消息给客户端
    strcpy(buffer, "Knock! Knock!\n");
    write(client_fd, buffer, strlen(buffer));

    // 接收客户端回复
    memset(buffer, 0, sizeof(buffer));
    read(client_fd, buffer, sizeof(buffer) - 1);
    printf("Thread ID: %lu, Client said: %s", tid, buffer);

    // 根据客户端回复发送不同响应
    if (strcmp(buffer, "Who's there?\n") == 0) {
        strcpy(buffer, "Oscar.\n");
        write(client_fd, buffer, strlen(buffer));
        // 再次接收客户端回复
        memset(buffer, 0, sizeof(buffer));
        read(client_fd, buffer, sizeof(buffer) - 1);
        printf("Thread ID: %lu, Client said: %s", tid, buffer);
        if (strcmp(buffer, "Oscar who?\n") == 0) {
            strcpy(buffer, "Oscar silly question, you get a silly answer.\n");
            write(client_fd, buffer, strlen(buffer));
        } else {
            strcpy(buffer, "I was expecting 'Oscar who?'.\n");
            write(client_fd, buffer, strlen(buffer));
        }
    } else {
        strcpy(buffer, "I was expecting 'Who's there?'.\n");
        write(client_fd, buffer, strlen(buffer));
    }

    close(client_fd);
    free(arg);
    return NULL;
}

int main(int argc, char *argv[]) {
    int sockfd, new_fd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t sin_size;
    pthread_t thread_id;

    // 创建套接字
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        error("Error creating socket");
    }

    // 初始化服务器地址结构体
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    server_addr.sin_addr.s_addr = INADDR_ANY;
    memset(server_addr.sin_zero, '\0', sizeof(server_addr.sin_zero));

    // 绑定套接字到指定地址和端口
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        error("Error binding");
    }

    // 监听端口，设置最大等待连接数
    if (listen(sockfd, BACKLOG) == -1) {
        error("Error listening");
    }

    printf("Server is waiting for connections...\n");

    while (1) {
        sin_size = sizeof(client_addr);
        // 接受客户端连接
        new_fd = accept(sockfd, (struct sockaddr *)&client_addr, &sin_size);
        if (new_fd == -1) {
            error("Error accepting connection");
        }
        ThreadArgs *args = (ThreadArgs *)malloc(sizeof(ThreadArgs));
        args->client_fd = new_fd;

        // 创建新线程来处理客户端连接
        if (pthread_create(&thread_id, NULL, handle_client, args)!= 0) {
            error("Error creating thread");
        }
        // 分离线程，让线程结束后自动释放资源
        pthread_detach(thread_id);
    }
    close(sockfd);
    return 0;
}

此时服务器开始运行并监听在指定的端口（代码中定义的PORT为3490），终端显示Server is waiting for connections...表示服务器正在等待连接。打开多个（至少两个）终端窗口，分别输入telnet localhost 3490来连接服务器：

连接成功后，每个客户端都会收到服务器发送的初始消息Knock! Knock!，然后可以按照 “knock knock” 的交互规则在客户端输入回复。输入Who's there?，按回车键后，在服务器运行的终端窗口中，会打印出每个客户端对应的线程 ID 以及客户端发送的消息等相关内容：