# 异步Http/WebSocket客户端

建议先阅读官方文档[异步Http/WebSocket客户端](https://wiki.swoole.com/wiki/page/p-http_client.html)章节

**一、为什么需要异步** 

通常我们进行 http 请求都是通过 curl 或者 file\_get\_contents，但是并发的性能都不好，都是同步执行，需要等待请求执行完成才能执行下一步操作，Swoole 内置的 swoole\_http\_client(Http 异步客户端)没有并发限制，当你的程序读取网络或磁盘时。swoole会加入到事件监听中，完全不需要等待，你的代码可以取做别的事情。当网络或磁盘读取完成，返回数据时，再继续向下执行你的代码。

**二、异步Http/WebSocket客户端** 

1、默认发送get及post请求

```
$host如果为域名底层需要进行一次DNS查询才能得到ip地址，这是阻塞IO，所以使用`Swoole\Async::dnsLookup`实现异步非阻塞
```

```php
<?php
//dns解析
Swoole\Async::dnsLookup("www.baidu.com", function ($domainName, $ip) {

    $client = new swoole_http_client($ip, 80);
   //设置请求头
    $client->setHeaders([
        'Accept' => 'text/html,application/xhtml+xml,application/xml',
        'Accept-Encoding' => 'gzip',
    ]);

    //发送get请求
    $client->get('/', function ($cli) {
        echo "Length: " . strlen($cli->body) . "\n";
        echo $cli->body;
    });
});

echo '是不是同步执行';
```

2、自定义请求类型

```php
$client = new swoole_http_client('218.64.129.244', 9500);
//设置请求头
$client->setHeaders([
    'Accept' => 'text/html,application/xhtml+xml,application/xml',
    'Accept-Encoding' => 'gzip',
]);

//自定义请求类型 PUT
$client->setMethod('PUT');
$client->setData(['name'=>'peter']);
$client->execute('/',function ($cli){
    var_dump($cli);

});
```

3.http请求改造升级为websocket

通过upgrade方法发起WebSocket握手请求，并将连接升级为WebSocket

```php
<?php

$client = new swoole_http_client('218.64.129.244', 9500);

//监听服务端给我们发送的数据
$client->on('message',function ($cli,$frame){
    var_dump($frame);
});

//websocket建立的是一个长连接
$client->upgrade('/',function ($cli){
    $cli->push('hello world');
});
```


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