用C语言代码完成：这个简单的网络聊天室服务器支持多个客户端同时连接，并能够实现客户端之间的聊天功能。客户端连接到服务器后，会收到一个欢迎消息，然后可以发送消息给其他客户端。服务器会将接收到的消息广播给所有客户端。

以下是一个简单的网络聊天室服务器的示例代码，使用C语言编写：

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

#define MAX_CLIENTS 10

// 定义客户端结构体
typedef struct {
    int socket;
    struct sockaddr_in address;
    pthread_t thread;
} client_t;

// 定义客户端列表
client_t clients[MAX_CLIENTS];

// 定义互斥锁
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

// 定义服务器地址和端口号
#define PORT 8888
#define ADDRESS "127.0.0.1"

// 定义广播消息函数
void broadcast_message(char *message, int sender_socket) {
    pthread_mutex_lock(&mutex);

    for (int i = 0; i < MAX_CLIENTS; i++) {
        if (clients[i].socket != 0 && clients[i].socket != sender_socket) {
            send(clients[i].socket, message, strlen(message), 0);
        }
    }

    pthread_mutex_unlock(&mutex);
}

// 定义客户端线程函数
void *client_thread(void *arg) {
    client_t *client = (client_t *)arg;

    printf("Client connected: %s:%d\n", inet_ntoa(client->address.sin_addr), ntohs(client->address.sin_port));

    // 发送欢迎消息
    char *welcome_message = "Welcome to the chatroom!\n";
    send(client->socket, welcome_message, strlen(welcome_message), 0);

    char message[1024];

    while (1) {
        // 接收客户端消息
        memset(message, 0, sizeof(message));
        int bytes_received = recv(client->socket, message, sizeof(message), 0);

        if (bytes_received <= 0) {
            break;
        }

        // 广播消息给其他客户端
        broadcast_message(message, client->socket);
    }

    // 客户端断开连接
    printf("Client disconnected: %s:%d\n", inet_ntoa(client->address.sin_addr), ntohs(client->address.sin_port));

    close(client->socket);
    client->socket = 0;

    pthread_exit(NULL);
}

int main(int argc, char **argv) {
    int server_socket;
    struct sockaddr_in server_address;

    // 创建socket对象
    server_socket = socket(AF_INET, SOCK_STREAM, 0);

    if (server_socket == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 设置地址和端口号
    server_address.sin_family = AF_INET;
    server_address.sin_addr.s_addr = inet_addr(ADDRESS);
    server_address.sin_port = htons(PORT);

    // 绑定地址和端口号
    if (bind(server_socket, (struct sockaddr *)&server_address, sizeof(server_address)) == -1) {
        perror("bind");
        exit(EXIT_FAILURE);
    }

    // 开始监听
    if (listen(server_socket, MAX_CLIENTS) == -1) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    printf("Server started on %s:%d\n", ADDRESS, PORT);

    while (1) {
        // 等待客户端连接
        struct sockaddr_in client_address;
        socklen_t client_address_length = sizeof(client_address);
        int client_socket = accept(server_socket, (struct sockaddr *)&client_address, &client_address_length);

        if (client_socket == -1) {
            perror("accept");
            exit(EXIT_FAILURE);
        }

        // 查找空闲客户端
        int index = -1;

        for (int i = 0; i < MAX_CLIENTS; i++) {
            if (clients[i].socket == 0) {
                index = i;
                break;
            }
        }

        if (index == -1) {
            printf("Too many clients\n");
            close(client_socket);
        } else {
            // 创建客户端线程
            clients[index].socket = client_socket;
            clients[index].address = client_address;
            pthread_create(&clients[index].thread, NULL, client_thread, &clients[index]);
        }
    }

    // 关闭socket
    close(server_socket);

    return 0;
}

这个简单的网络聊天室服务器支持多个客户端同时连接，并能够实现客户端之间的聊天功能。客户端连接到服务器后，会收到一个欢迎消息，然后可以发送消息给其他客户端。服务器会将接收到的消息广播给所有客户端。同时，服务器使用了互斥锁来保证线程安全，避免多个线程同时访问共享变量造成的数据竞争问题。