用c语言写一个socket的多对多程序server端

好的，以下是一个简单的多对多服务器端程序的C语言代码示例：

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

#define BUF_SIZE 100
#define NAME_SIZE 20
#define MAX_CLIENTS 10

void error_handling(char *message);
void send_message(char *message, int len, int sender);
void remove_client(int client);

int clients[MAX_CLIENTS];
char name_arr[MAX_CLIENTS][NAME_SIZE];
char message[BUF_SIZE];
fd_set reads, copy_reads;

int main(int argc, char *argv[]) {
    int serv_sock, client_sock;
    struct sockaddr_in serv_addr, client_addr;
    socklen_t client_addr_size;
    int str_len, i, j, max_fd;
    char name[NAME_SIZE];
    struct timeval timeout;
    int fd_num, fd;

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

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if (serv_sock == -1) {
        error_handling("socket() error");
    }

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

    if (bind(serv_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1) {
        error_handling("bind() error");
    }

    if (listen(serv_sock, 5) == -1) {
        error_handling("listen() error");
    }

    FD_ZERO(&reads);
    FD_SET(serv_sock, &reads);
    max_fd = serv_sock;

    while (1) {
        copy_reads = reads;
        timeout.tv_sec = 5;
        timeout.tv_usec = 5000;

        fd_num = select(max_fd + 1, &copy_reads, NULL, NULL, &timeout);
        if (fd_num == -1) {
            break;
        }
        if (fd_num == 0) {
            continue;
        }

        for (fd = 0; fd < max_fd + 1; fd++) {
            if (FD_ISSET(fd, &copy_reads)) {
                if (fd == serv_sock) {
                    client_addr_size = sizeof(client_addr);
                    client_sock = accept(serv_sock, (struct sockaddr *)&client_addr, &client_addr_size);
                    FD_SET(client_sock, &reads);
                    if (client_sock > max_fd) {
                        max_fd = client_sock;
                    }
                    printf("Connected client: %d\n", client_sock);
                    sprintf(name, "[%d]", client_sock);
                    strcpy(name_arr[client_sock], name);
                    clients[client_sock] = 1;
                } else {
                    str_len = read(fd, message, BUF_SIZE);
                    if (str_len == 0) {
                        remove_client(fd);
                        FD_CLR(fd, &reads);
                    } else {
                        send_message(message, str_len, fd);
                    }
                }
            }
        }
    }

    close(serv_sock);
    return 0;
}

void error_handling(char *message) {
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

void send_message(char *message, int len, int sender) {
    int i;
    for (i = 0; i < max_fd + 1; i++) {
        if (FD_ISSET(i, &reads)) {
            if (i != sender && i != serv_sock) {
                write(i, name_arr[sender], strlen(name_arr[sender]));
                write(i, " ", 1);
                write(i, message, len);
            }
        }
    }
}

void remove_client(int client) {
    int i;
    close(client);
    clients[client] = 0;
    for (i = 0; i < MAX_CLIENTS; i++) {
        if (clients[i] == 1) {
            FD_SET(i, &reads);
        }
    }
    printf("Removed client: %d\n", client);
}

这个程序使用`socket()`函数创建一个TCP套接字，然后使用`bind()`函数将其绑定到指定的端口上。然后使用`listen()`函数开始监听客户端连接请求。当有客户端连接时，使用`accept()`函数接受连接请求并将客户端套接字加入到`fd_set`集合中。使用`select()`函数监听所有连接的套接字，如果有套接字可读，使用`read()`函数读取客户端的消息并广播给其他客户端。如果客户端关闭连接，将其从`fd_set`集合中移除并关闭套接字。

请注意，这个程序只是一个简单的示例，没有进行错误处理和线程安全处理。如果需要在实际应用中使用，请进行必要的改进。