我需要的是一个用C++或者JAVA实现的，你可以给出一个吗

当然，我可以为您提供一个简单的C++实现的即时消息传递实用程序的模板，您可以根据您的需求进行修改和扩展：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>
#include <thread>
#include <vector>

using namespace std;

#define MAX_BUF_SIZE 1024
#define DEFAULT_PORT 1234

// 客户端类
class Client {
public:
    Client(const char* addr, int port) {
        // 创建socket
        if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
            perror("socket");
            exit(EXIT_FAILURE);
        }

        // 设置服务器地址和端口号
        memset(&server_addr, 0, sizeof(server_addr));
        server_addr.sin_family = AF_INET;
        server_addr.sin_port = htons(port);
        if (inet_pton(AF_INET, addr, &server_addr.sin_addr) <= 0) {
            perror("inet_pton");
            exit(EXIT_FAILURE);
        }

        // 连接服务器
        if (connect(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
            perror("connect");
            exit(EXIT_FAILURE);
        }

        // 启动接收消息线程
        recv_thread = thread(&Client::recv_msg, this);
    }

    // 发送消息
    void send_msg(const char* msg) {
        send(sockfd, msg, strlen(msg), 0);
    }

    // 接收消息
    void recv_msg() {
        char buf[MAX_BUF_SIZE] = {0};
        while (true) {
            int n = recv(sockfd, buf, MAX_BUF_SIZE, 0);
            if (n <= 0) {
                break;
            }
            printf("%s\n", buf);
            memset(buf, 0, MAX_BUF_SIZE);
        }
    }

private:
    int sockfd;
    struct sockaddr_in server_addr;
    thread recv_thread;
};

// 服务器类
class Server {
public:
    Server(int port) {
        // 创建socket
        if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
            perror("socket");
            exit(EXIT_FAILURE);
        }

        // 设置服务器地址和端口号
        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);

        // 绑定socket和地址
        if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
            perror("bind");
            exit(EXIT_FAILURE);
        }

        // 监听socket
        if (listen(sockfd, 5) < 0) {
            perror("listen");
            exit(EXIT_FAILURE);
        }
    }

    // 处理客户端连接
    void handle_client(int fd) {
        char username[MAX_BUF_SIZE] = {0};
        char password[MAX_BUF_SIZE] = {0};
        if (recv(fd, username, MAX_BUF_SIZE, 0) <= 0 || recv(fd, password, MAX_BUF_SIZE, 0) <= 0) {
            close(fd);
            return;
        }
        if (authenticate(username, password)) {
            printf("%s connected\n", username);
            clients.push_back(fd);
            while (true) {
                char buf[MAX_BUF_SIZE] = {0};
                int n = recv(fd, buf, MAX_BUF_SIZE, 0);
                if (n <= 0) {
                    break;
                }
                // 将消息广播给其他客户端
                for (int i = 0; i < clients.size(); i++) {
                    if (clients[i] != fd) {
                        send(clients[i], buf, strlen(buf), 0);
                    }
                }
            }
            printf("%s disconnected\n", username);
            clients.erase(remove(clients.begin(), clients.end(), fd), clients.end());
        } else {
            send(fd, "Authentication failed", strlen("Authentication failed"), 0);
            close(fd);
        }
    }

    // 认证用户
    bool authenticate(const char* username, const char* password) {
        // TODO: 在此处添加您的认证逻辑
        return true;
    }

    // 启动服务器
    void start() {
        while (true) {
            struct sockaddr_in client_addr;
            socklen_t client_len = sizeof(client_addr);
            int client_fd = accept(sockfd, (struct sockaddr*)&client_addr, &client_len);
            if (client_fd < 0) {
                perror("accept");
                continue;
            }
            thread(&Server::handle_client, this, client_fd).detach();
        }
    }

private:
    int sockfd;
    struct sockaddr_in server_addr;
    vector<int> clients;
};

int main(int argc, char* argv[]) {
    if (argc == 2) {
        Server server(atoi(argv[1]));
        server.start();
    } else if (argc == 3) {
        Client client(argv[1], atoi(argv[2]));
        char msg[MAX_BUF_SIZE];
        while (fgets(msg, MAX_BUF_SIZE, stdin) != NULL) {
            client.send_msg(msg);
        }
    } else {
        printf("Usage: %s [port] (for server)\n", argv[0]);
        printf("       %s [address] [port] (for client)\n", argv[0]);
        return 1;
    }
    return 0;
}

上述代码提供了一个简单的服务器和客户端实现，其中服务器支持多个客户端连接，并且客户端可以发送消息给其他客户端。您可以根据您的需求对其进行修改和扩展，例如添加认证、加密、持久化存储等功能。