作为socket长连接服务器，Swoole如果要做到主动对已经连接过来的，用户uid=123的那个用户，推送一条消息应该怎么写？

<code><?php $serv = new <a style='color:#f60; text-decoration:underline;' href="https://www.php.cn/zt/53189.html" target="_blank">swoole_server("127.0.0.1", 1024);
$serv-&gt;set(array(
    'worker_num' =&gt; 8,   //工作进程数量
    'daemonize' =&gt; false, //是否作为守护进程
));

$shmid = shm_attach(getmypid(), 1024*66); # allocate 66kB for shared memory
define("SHARED_UID_CONNECTION_MAP", 12);
shm_put_var($shmid,SHARED_UID_CONNECTION_MAP, []);

$serv-&gt;on('connect', function ($serv, $fd) use($shmid) {
    echo "Client:Connect.\n";
});

$serv-&gt;on('receive', function ($serv, $fd, $from_id, $data) use($shmid)  {

    $serv-&gt;send($fd, 'Swoole: '.$data);
    // $serv-&gt;close($fd);

    $trimdata = trim($data);
    if ($trimdata == 'i am lucky man') {
        $map = shm_get_var($shmid,SHARED_UID_CONNECTION_MAP);
        $map[] = $fd;   #$map[$uidFromData] = $fd;
        shm_put_var($shmid,SHARED_UID_CONNECTION_MAP, $map);
    }


    if ($trimdata == 'broadcast to lucky man') {
        $map = shm_get_var($shmid,SHARED_UID_CONNECTION_MAP);
        // var_dump($map); $ $map is array whose valuse is int $fd
        foreach($map as $fd) {
            $serv-&gt;send($fd, "some body broadcast to you luck man");
        }
    }

    # broadcast to all users
    // $start_fd = 0;
    // while(true)
    // {
    //     $conn_list = $serv-&gt;connection_list($start_fd, 10);
    //     if($conn_list===false or count($conn_list) === 0)
    //     {
    //         echo "finish\n";
    //         break;
    //     }
    //     $start_fd = end($conn_list);
    //     var_dump($conn_list);
    //     foreach($conn_list as $fd)
    //     {
    //         $serv-&gt;send($fd, "broadcast");
    //     }
    // }

    // var_dump($serv-&gt;connections);
    // foreach ($serv-&gt;connections as $k =&gt; $v) {
    //    $lk = [$k,$v];
    //    var_dump($lk);
    // }

});
$serv-&gt;on('close', function ($serv, $fd) {
    echo "Client: Close.\n";
});
$serv-&gt;start();

</code>