What is the use of swoole client?

$client = new swoole_client(SWOOLE_SOCK_TCP);

if (!$client->connect('127.0.0.1', 9501, -1))
{
    exit("connect failed. Error: {$client->errCode}\n");
}

$client->send("hello world\n");

echo $client->recv();

$client->close();

$client = new Swoole\Client(SWOOLE_SOCK_TCP, SWOOLE_SOCK_ASYNC);
$client->on("connect", function(swoole_client $cli) {
    $cli->send("GET / HTTP/1.1\r\n\r\n");
});
$client->on("receive", function(swoole_client $cli, $data){
    echo "Receive: $data";
    $cli->send(str_repeat('A', 100)."\n");
    sleep(1);
});
$client->on("error", function(swoole_client $cli){
    echo "error\n";
});
$client->on("close", function(swoole_client $cli){
    echo "Connection close\n";
});
$client->connect('127.0.0.1', 9501);