c语言socket 的服务端和多个客户端通信

要实现C语言Socket的服务端和多个客户端通信，可以使用多线程技术，为每个客户端连接创建一个新的线程来处理通信。

以下是一个简单的示例代码：

1. 服务端

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

#define MAX_CLIENTS 10   // 最大客户端数量
#define PORT 8888        // 监听端口号

void *client_handler(void *arg);

int main() {
    int server_fd, client_fd, opt = 1;
    struct sockaddr_in server_addr, client_addr;
    socklen_t addr_len = sizeof(struct sockaddr_in);
    pthread_t tid[MAX_CLIENTS];
    int i, ret;

    // 创建服务器Socket
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // 设置Socket选项，允许地址重用
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt failed");
        exit(EXIT_FAILURE);
    }

    // 绑定地址和端口号
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(PORT);

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

    // 监听端口
    if (listen(server_fd, MAX_CLIENTS) < 0) {
        perror("listen failed");
        exit(EXIT_FAILURE);
    }

    printf("Server: listening on port %d\n", PORT);

    // 接受客户端连接并创建线程处理通信
    while (1) {
        if ((client_fd = accept(server_fd, (struct sockaddr *)&client_addr, &addr_len)) < 0) {
            perror("accept failed");
            continue;
        }

        printf("Server: new client connected, IP address: %s, port number: %d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));

        // 创建新线程处理客户端通信
        for (i = 0; i < MAX_CLIENTS; i++) {
            if (tid[i] == 0) {
                if (pthread_create(&tid[i], NULL, client_handler, (void *)&client_fd) < 0) {
                    perror("pthread_create failed");
                    break;
                }
                break;
            }
        }

        // 客户端数量已达到最大值，拒绝新连接
        if (i == MAX_CLIENTS) {
            printf("Server: max client connections reached, new connection rejected\n");
            close(client_fd);
        }
    }

    return 0;
}

// 客户端处理函数
void *client_handler(void *arg) {
    int client_fd = *(int *)arg;
    char buffer[1024] = {0};
    int ret;

    while (1) {
        memset(buffer, 0, sizeof(buffer));

        // 接收客户端消息
        if ((ret = recv(client_fd, buffer, sizeof(buffer), 0)) <= 0) {
            if (ret == 0) {
                printf("Server: client disconnected\n");
            } else {
                perror("recv failed");
            }
            break;
        }

        // 处理客户端消息
        printf("Server: received message from client: %s\n", buffer);

        // 发送响应消息
        if (send(client_fd, buffer, strlen(buffer), 0) < 0) {
            perror("send failed");
            break;
        }
    }

    // 关闭连接
    close(client_fd);
    pthread_exit(NULL);
}

2. 客户端

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

#define SERVER_IP "127.0.0.1"  // 服务器IP地址
#define SERVER_PORT 8888       // 服务器端口号

int main() {
    int client_fd;
    struct sockaddr_in server_addr;
    char buffer[1024] = {0};
    int ret;

    // 创建客户端Socket
    if ((client_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // 连接服务器
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    server_addr.sin_port = htons(SERVER_PORT);

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

    printf("Client: connected to server, IP address: %s, port number: %d\n", SERVER_IP, SERVER_PORT);

    // 发送消息给服务器
    strcpy(buffer, "Hello, server!");
    if (send(client_fd, buffer, strlen(buffer), 0) < 0) {
        perror("send failed");
        exit(EXIT_FAILURE);
    }

    // 接收服务器响应消息
    memset(buffer, 0, sizeof(buffer));
    if ((ret = recv(client_fd, buffer, sizeof(buffer), 0)) < 0) {
        perror("recv failed");
        exit(EXIT_FAILURE);
    }

    printf("Client: received message from server: %s\n", buffer);

    // 关闭连接
    close(client_fd);

    return 0;
}