Laravel使用composer安装Agent

Question

我想安装Laravel 4 User Agent我在"jenssegers/agent": "*"部分添加required。运行此命令后出现此错误。

composer update

结果：

Loading composer repositories with package information
Updating dependencies (including require-dev)


  [Composer\Downloader\TransportException]                                                                                                                                                     
  The "http://packagist.org/p/symfony/event-dispatcher$db57a4209d50296c5b7b06f4c34cd7e3ba3f2e0e02ec4c687917a2ccbac7faca.json" file could not be downloaded: php_network_getaddresses: getaddr  
  info failed: Name or service not known                                                                                                                                                       
  failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known                                                                                               

update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-plugins] [--no-custom-installers] [--no-scripts] [--no-progress] [--with-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [packages1] ... [packagesN]

我的composer.json内容：

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "require": {
        "laravel/framework": "4.1.*",
        "jenssegers/agent": "*"
    },
    "autoload": {
        "classmap": [
            "app/commands",
            "app/controllers",
            "app/models",
            "app/database/migrations",
            "app/database/seeds",
            "app/tests/TestCase.php"
        ]
    },
    "scripts": {
        "post-install-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "php artisan clear-compiled",
            "php artisan optimize"
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ]
    },
    "config": {
        "preferred-install": "dist"
    },
    "minimum-stability": "stable"
}