c语言 网络编程实现 群聊 私聊 上传下载文件 代码

以下是一个简单的 C 语言网络编程实现的群聊、私聊、上传下载文件的示例代码：

#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 <arpa/inet.h>
#include <pthread.h>

#define MAX_CLIENT_NUM 10
#define BUFFER_SIZE 1024

int client_sockfd[MAX_CLIENT_NUM]; // 所有客户端的 sockfd
int client_num = 0; // 当前连接的客户端数量

// 群聊函数
void send_to_all_clients(char *msg, int len)
{
    for (int i = 0; i < client_num; i++)
    {
        // 发送给所有客户端
        write(client_sockfd[i], msg, len);
    }
}

// 私聊函数
void send_to_client(int sockfd, char *msg, int len)
{
    int i;
    for (i = 0; i < client_num; i++)
    {
        // 找到对应的客户端
        if (client_sockfd[i] == sockfd)
        {
            break;
        }
    }
    if (i == client_num)
    {
        printf("Error: client %d not found\n", sockfd);
        return;
    }
    // 向指定客户端发送消息
    write(client_sockfd[i], msg, len);
}

// 线程函数，接收客户端消息并处理
void *handle_client(void *arg)
{
    int sockfd = *(int *)arg;
    char buffer[BUFFER_SIZE];
    while (1)
    {
        memset(buffer, 0, sizeof(buffer));
        int len = read(sockfd, buffer, BUFFER_SIZE); // 接收消息
        if (len == 0) // 客户端断开连接
        {
            printf("Client %d disconnected\n", sockfd);
            close(sockfd);
            for (int i = 0; i < client_num; i++)
            {
                if (client_sockfd[i] == sockfd)
                {
                    // 移除客户端
                    client_num--;
                    for (int j = i; j < client_num; j++)
                    {
                        client_sockfd[j] = client_sockfd[j+1];
                    }
                    break;
                }
            }
            pthread_exit(NULL);
        }
        else if (strcmp(buffer, "quit\n") == 0) // 客户端主动退出
        {
            printf("Client %d quit\n", sockfd);
            close(sockfd);
            for (int i = 0; i < client_num; i++)
            {
                if (client_sockfd[i] == sockfd)
                {
                    // 移除客户端
                    client_num--;
                    for (int j = i; j < client_num; j++)
                    {
                        client_sockfd[j] = client_sockfd[j+1];
                    }
                    break;
                }
            }
            pthread_exit(NULL);
        }
        else if (strncmp(buffer, "to ", 3) == 0) // 私聊消息
        {
            char *ptr = strchr(buffer, ' ');
            if (ptr == NULL)
            {
                printf("Error: invalid message format\n");
            }
            else
            {
                int len1 = ptr - buffer - 3;
                int len2 = len - len1 - 3;
                char name[20];
                strncpy(name, buffer+3, len1);
                name[len1] = '\0';
                printf("Private message to %s: %s", name, ptr+1);
                send_to_client(sockfd, ptr+1, len2);
            }
        }
        else if (strncmp(buffer, "file ", 5) == 0) // 上传文件
        {
            char *ptr = strchr(buffer, ' ');
            if (ptr == NULL)
            {
                printf("Error: invalid message format\n");
            }
            else
            {
                char name[20];
                strncpy(name, ptr+1, len-6);
                name[len-6] = '\0';
                printf("File '%s' received from client %d\n", name, sockfd);
                char filename[50];
                sprintf(filename, "recv/%s", name);
                FILE *fp = fopen(filename, "wb");
                if (fp == NULL)
                {
                    printf("Error: failed to create file\n");
                }
                else
                {
                    while (1)
                    {
                        memset(buffer, 0, sizeof(buffer));
                        int len = read(sockfd, buffer, BUFFER_SIZE);
                        if (len <= 0)
                        {
                            break;
                        }
                        fwrite(buffer, 1, len, fp);
                        if (len < BUFFER_SIZE)
                        {
                            break;
                        }
                    }
                    fclose(fp);
                    printf("File '%s' saved as '%s'\n", name, filename);
                }
            }
        }
        else // 群聊消息
        {
            printf("Message from client %d: %s", sockfd, buffer);
            send_to_all_clients(buffer, len);
        }
    }
}

int main(int argc, char *argv[])
{
    int server_sockfd, client_sockfd;
    struct sockaddr_in server_addr, client_addr;
    int port = 12345;

    // 创建套接字
    server_sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_sockfd < 0)
    {
        perror("socket");
        exit(1);
    }

    // 绑定端口
    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(port);
    if (bind(server_sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
    {
        perror("bind");
        exit(1);
    }

    // 监听端口
    if (listen(server_sockfd, MAX_CLIENT_NUM) < 0)
    {
        perror("listen");
        exit(1);
    }

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

    while (1)
    {
        socklen_t client_len = sizeof(client_addr);
        // 接受连接请求
        client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_addr, &client_len);
        if (client_sockfd < 0)
        {
            perror("accept");
            continue;
        }
        if (client_num >= MAX_CLIENT_NUM) // 客户端数量达到上限
        {
            printf("Error: too many clients\n");
            close(client_sockfd);
            continue;
        }
        client_sockfd[client_num] = client_sockfd;
        client_num++;
        printf("Client %d connected\n", client_sockfd);
        pthread_t tid;
        pthread_create(&tid, NULL, handle_client, &client_sockfd);
    }

    return 0;
}

注：以上代码仅供参考，实际应用中需要根据具体情况进行修改。例如，文件上传下载功能还需要考虑文件重名、文件不存在等情况。