int main(int argc, char *argv[]) { int sock; /* Socket */ struct sockaddr_in broadcastAddr; /* Broadcast Address */ /* Create a best-effort datagram socket using UDP */ if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) { perror("socket failed"); exit(EXIT_FAILURE); } /* Construct bind structure */ memset(&broadcastAddr, 0, sizeof(broadcastAddr)); /* Zero out structure */ broadcastAddr.sin_family = AF_INET; /* Internet address family */ broadcastAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */ broadcastAddr.sin_port = htons(PORT); /* Broadcast port */ /* Bind to the broadcast port */ if (bind(sock, (struct sockaddr *) &broadcastAddr, sizeof(broadcastAddr)) < 0) { perror("bind failed"); exit(EXIT_FAILURE); } char recvString[MAXRECVSTRING + 1]; int recvStringLen; int count = 0; while(1) { if ((recvStringLen = recvfrom(sock, recvString, MAXRECVSTRING, 0, NULL, 0)) < 0) { perror("recvfrom failed"); exit(EXIT_FAILURE); } switch(recvString[0]) { case '1': printf("S1\n"); break; case '2': printf("S2\n"); break; case '3': printf("S3\n"); break; default: continue; } } close(sock); exit(0); }

这是一个使用UDP协议的C语言网络编程例子，通过创建一个socket和绑定一个广播地址，可以接收从其他主机发送的广播消息。在while循环中，通过recvfrom函数来接收消息，并通过switch语句来判断接收到的消息类型，并进行相应的处理。如果接收到的消息不是指定的类型，则继续等待接收下一条消息。最后，通过close函数关闭socket连接。

相关问题

C/C++ 编写一个服务器与客户端的群聊

以下是一个简单的基于TCP协议的服务器与客户端的群聊实现。该程序使用了多线程来支持多个客户端同时连接。

服务器代码（chat_server.c）：

#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 <pthread.h>

#define MAX_CLIENTS 10
#define BUFFER_SIZE 1024

int clients[MAX_CLIENTS];
int num_clients = 0;
pthread_mutex_t clients_mutex = PTHREAD_MUTEX_INITIALIZER;

void broadcast_message(char *message, int sender) {
    pthread_mutex_lock(&clients_mutex);
    for (int i = 0; i < num_clients; i++) {
        if (clients[i] != sender) {
            send(clients[i], message, strlen(message), 0);
        }
    }
    pthread_mutex_unlock(&clients_mutex);
}

void *client_thread(void *arg) {
    int client_fd = *(int*)arg;
    char buffer[BUFFER_SIZE];

    pthread_mutex_lock(&clients_mutex);
    clients[num_clients++] = client_fd;
    pthread_mutex_unlock(&clients_mutex);

    while (1) {
        int bytes_read = recv(client_fd, buffer, BUFFER_SIZE, 0);
        if (bytes_read <= 0) {
            pthread_mutex_lock(&clients_mutex);
            for (int i = 0; i < num_clients; i++) {
                if (clients[i] == client_fd) {
                    clients[i] = -1;
                    break;
                }
            }
            pthread_mutex_unlock(&clients_mutex);
            close(client_fd);
            return NULL;
        }
        buffer[bytes_read] = '\0';
        broadcast_message(buffer, client_fd);
    }
}

int main(int argc, char *argv[]) {
    int server_fd, client_fd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t client_len = sizeof(client_addr);
    pthread_t tid;

    if (argc != 2) {
        printf("Usage: %s <port>\n", argv[0]);
        exit(1);
    }

    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket");
        exit(1);
    }

    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(atoi(argv[1]));

    if (bind(server_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind");
        exit(1);
    }

    if (listen(server_fd, MAX_CLIENTS) < 0) {
        perror("listen");
        exit(1);
    }

    printf("Server listening on port %s...\n", argv[1]);

    while (1) {
        client_fd = accept(server_fd, (struct sockaddr*)&client_addr, &client_len);
        if (client_fd < 0) {
            perror("accept");
            exit(1);
        }
        pthread_create(&tid, NULL, client_thread, &client_fd);
    }

    return 0;
}

客户端代码（chat_client.c）：

#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 <netdb.h>

#define BUFFER_SIZE 1024

int main(int argc, char *argv[]) {
    int client_fd, port;
    char buffer[BUFFER_SIZE];
    struct hostent *server;
    struct sockaddr_in server_addr;

    if (argc != 3) {
        printf("Usage: %s <hostname> <port>\n", argv[0]);
        exit(1);
    }

    port = atoi(argv[2]);
    server = gethostbyname(argv[1]);
    if (server == NULL) {
        fprintf(stderr, "Error: no such host\n");
        exit(1);
    }

    client_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (client_fd < 0) {
        perror("socket");
        exit(1);
    }

    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    memcpy(&server_addr.sin_addr.s_addr, server->h_addr, server->h_length);
    server_addr.sin_port = htons(port);

    if (connect(client_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("connect");
        exit(1);
    }

    printf("Connected to server %s:%d\n", argv[1], port);

    while (1) {
        printf("> ");
        fgets(buffer, BUFFER_SIZE, stdin);
        send(client_fd, buffer, strlen(buffer), 0);
    }

    return 0;
}

编译方法：

gcc -o chat_server chat_server.c -lpthread
gcc -o chat_client chat_client.c

运行方法：

./chat_server <port>
./chat_client <hostname> <port>

其中，`<port>`是服务器监听的端口号，`<hostname>`是服务器的主机名或IP地址。客户端连接服务器后，可以输入任意文本并发送到服务器，服务器会将该文本广播给所有连接的客户端。

利用setsocketopt()使用嵌套字支持广播，并编写两个程序，其中一个发送广播数据，另一个接收广播数据。

好的，我会根据你的要求回答你的问题。以下是利用setsocketopt()使用嵌套字支持广播的步骤：

1. 创建一个 UDP 套接字

   int sockfd = socket(AF_INET, SOCK_DGRAM, 0);

2. 设置套接字选项，使其支持广播

   int broadcast = 1;
   setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast));

3. 绑定 IP 地址和端口号

   struct sockaddr_in addr;
   addr.sin_family = AF_INET;
   addr.sin_port = htons(PORT);  // PORT 为自定义的端口号
   addr.sin_addr.s_addr = htonl(INADDR_ANY);  // 使用 INADDR_ANY 表示可以接收来自任意 IP 地址的广播数据

   bind(sockfd, (struct sockaddr *)&addr, sizeof(addr));

4. 发送广播数据

   char buffer[MAXBUF];
   memset(buffer, 0, MAXBUF);
   strcpy(buffer, "Hello, world!");  // 自定义广播数据

   struct sockaddr_in broadcast_addr;
   broadcast_addr.sin_family = AF_INET;
   broadcast_addr.sin_port = htons(PORT);  // 广播的目标端口号
   broadcast_addr.sin_addr.s_addr = inet_addr("255.255.255.255");  // 广播的目标 IP 地址

   sendto(sockfd, buffer, strlen(buffer), 0, (struct sockaddr *)&broadcast_addr, sizeof(broadcast_addr));

5. 接收广播数据

   struct sockaddr_in client_addr;
   socklen_t client_addr_len = sizeof(client_addr);

   char buffer[MAXBUF];
   memset(buffer, 0, MAXBUF);

   int n = recvfrom(sockfd, buffer, MAXBUF, 0, (struct sockaddr *)&client_addr, &client_addr_len);

   // 处理接收到的广播数据
   printf("Received broadcast message: %s\n", buffer);

下面是两个程序的代码，一个发送广播数据，另一个接收广播数据：

发送广播数据的程序：

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

#define PORT 12345
#define MAXBUF 1024

int main(int argc, char *argv[]) {
    // 创建 UDP 套接字
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }

    // 设置套接字选项，使其支持广播
    int broadcast = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast));

    // 绑定 IP 地址和端口号
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        perror("bind");
        exit(1);
    }

    // 发送广播数据
    char buffer[MAXBUF];
    memset(buffer, 0, MAXBUF);
    strcpy(buffer, "Hello, world!");

    struct sockaddr_in broadcast_addr;
    broadcast_addr.sin_family = AF_INET;
    broadcast_addr.sin_port = htons(PORT);
    broadcast_addr.sin_addr.s_addr = inet_addr("255.255.255.255");

    sendto(sockfd, buffer, strlen(buffer), 0, (struct sockaddr *)&broadcast_addr, sizeof(broadcast_addr));

    printf("Sent broadcast message: %s\n", buffer);

    close(sockfd);

    return 0;
}

接收广播数据的程序：

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

#define PORT 12345
#define MAXBUF 1024

int main(int argc, char *argv[]) {
    // 创建 UDP 套接字
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }

    // 设置套接字选项，使其支持广播
    int broadcast = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast));

    // 绑定 IP 地址和端口号
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        perror("bind");
        exit(1);
    }

    // 接收广播数据
    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);

    char buffer[MAXBUF];
    memset(buffer, 0, MAXBUF);

    int n = recvfrom(sockfd, buffer, MAXBUF, 0, (struct sockaddr *)&client_addr, &client_addr_len);

    // 处理接收到的广播数据
    printf("Received broadcast message: %s\n", buffer);

    close(sockfd);

    return 0;
}