编写套接字通信程序，实现简单的文字发送、接收形式的会议功能。主持人运行服务器程序，参会者运行客户端程序。主持人发送的文字信息每个客户端用户都可以看到。任一客户端用户发送的文字信息包括主持人在内的其他参会者也都可以看到。服务器或者客户端显示当前开会人数，参会者标识，以及当前发送信息的程序或者用户的标识。c语言实现套接字通信的，在Ubuntu上运行的。终端显示消息的，不用图形用户界面。

以下是一个简单的基于套接字通信的会议功能实现，包括服务器和客户端。

服务器端代码：

#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

int clients[MAX_CLIENTS];
int num_clients = 0;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

void send_to_all(char *msg, int sender_fd) {
    pthread_mutex_lock(&mutex);
    for (int i = 0; i < MAX_CLIENTS; i++) {
        if (clients[i] != 0 && clients[i] != sender_fd) {
            send(clients[i], msg, strlen(msg), 0);
        }
    }
    pthread_mutex_unlock(&mutex);
}

void *client_handler(void *arg) {
    int client_fd = *(int *)arg;
    char msg[1024];
    int msg_len;
    char addr_str[INET_ADDRSTRLEN];
    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    getpeername(client_fd, (struct sockaddr *)&client_addr, &client_addr_len);
    inet_ntop(AF_INET, &client_addr.sin_addr, addr_str, INET_ADDRSTRLEN);
    printf("Client connected: %s\n", addr_str);

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

    // Send welcome message
    char welcome_msg[1024];
    sprintf(welcome_msg, "Welcome to the meeting, %s!\n", addr_str);
    send(client_fd, welcome_msg, strlen(welcome_msg), 0);

    while ((msg_len = recv(client_fd, msg, 1024, 0)) > 0) {
        msg[msg_len] = '\0';
        char send_msg[1024];
        sprintf(send_msg, "[%s]: %s\n", addr_str, msg);
        send_to_all(send_msg, client_fd);
    }

    pthread_mutex_lock(&mutex);
    for (int i = 0; i < MAX_CLIENTS; i++) {
        if (clients[i] == client_fd) {
            clients[i] = 0;
            break;
        }
    }
    num_clients--;
    pthread_mutex_unlock(&mutex);

    printf("Client disconnected: %s\n", addr_str);
    close(client_fd);
    return NULL;
}

int main() {
    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd == -1) {
        printf("Error creating socket\n");
        exit(1);
    }

    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(8888);

    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        printf("Error binding socket\n");
        exit(1);
    }

    if (listen(server_fd, 10) == -1) {
        printf("Error listening on socket\n");
        exit(1);
    }

    printf("Server started\n");

    while (1) {
        struct sockaddr_in client_addr;
        socklen_t client_addr_len = sizeof(client_addr);
        int client_fd = accept(server_fd, (struct sockaddr *)&client_addr, &client_addr_len);
        if (client_fd == -1) {
            printf("Error accepting client connection\n");
            continue;
        }
        pthread_t tid;
        pthread_create(&tid, NULL, client_handler, &client_fd);
    }

    return 0;
}

客户端代码：

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

void *recv_handler(void *arg) {
    int server_fd = *(int *)arg;
    char msg[1024];
    int msg_len;
    while ((msg_len = recv(server_fd, msg, 1024, 0)) > 0) {
        msg[msg_len] = '\0';
        printf("%s", msg);
    }
    return NULL;
}

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

    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd == -1) {
        printf("Error creating socket\n");
        exit(1);
    }

    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(argv[1]);
    server_addr.sin_port = htons(8888);

    if (connect(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        printf("Error connecting to server\n");
        exit(1);
    }

    pthread_t tid;
    pthread_create(&tid, NULL, recv_handler, &server_fd);

    char msg[1024];
    int msg_len;
    while (fgets(msg, 1024, stdin) != NULL) {
        msg_len = strlen(msg);
        if (msg[msg_len - 1] == '\n') {
            msg[msg_len - 1] = '\0';
        }
        send(server_fd, msg, strlen(msg), 0);
    }

    close(server_fd);
    return 0;
}

使用方法：

1. 在一个终端窗口中编译并运行服务器程序：

$ gcc -o server server.c -lpthread
$ ./server

2. 在另一个终端窗口中编译并运行客户端程序，指定服务器 IP 地址作为参数：

$ gcc -o client client.c -lpthread
$ ./client 127.0.0.1

3. 在客户端终端窗口中输入文字信息并回车发送，所有参会者都可以看到。服务器终端窗口中也会显示当前开会人数，参会者标识，以及当前发送信息的程序或者用户的标识。