在我的composer.json中，我更新了以下行：
"require": {
"<x>/<y>" : "dev-<newBranch>"
}
当我调用composer update <x>/<y>时，出现此错误：
无法下载"https://repo.packagist.org/packages.json"文件：无法打开流：连接超时'
可以从我的浏览器访问给定的 URL，没有任何问题。
包装和分支可在包装师上找到。
输出composer update <x>/<y> -vv
异常跟踪：
(( 在 phar:///usr/local/bin/composer/src/Composer/Util/RemoteFilesystem.php:550 Composer\Util\RemoteFilesystem->get(( at phar:///usr/local/bin/composer/src/Composer/Util/RemoteFilesystem.php:101 Composer\Util\RemoteFilesystem->getContent(( at phar:///usr/local/bin/composer/src/Composer/Repository/ComposerRepository.php:682 Composer\Repository\ComposerRepository->fetchFile(( at phar:///usr/local/bin/composer/src/Composer/Repository/ComposerRepository.php:497 Composer\Repository\ComposerRepository->loadRootServerFile(( at phar:///usr/local/bin/composer/src/Composer/Repository/ComposerRepository.php:276 Composer\Repository\ComposerRepository->hasProviders(( at phar:///usr/local/bin/composer/src/Composer/DependencyResolver/Pool.php:99 Composer\DependencyResolver\Pool->addRepository(( at phar:///usr/local/bin/composer/src/Composer/Installer.php:378 Composer\Installer->doInstall(( at phar:///usr/local/bin/composer/src/Composer/Installer.php:228 Composer\Installer->run(( at phar:///usr/local/bin/composer/src/Composer/Command/UpdateCommand.php:162 Composer\Command\UpdateCommand->execute(( at phar:///usr/local/bin/composer/vendor/symfony/console/Command/Command.php:241 Symfony\Component\Console\Command\Command->run(( at phar:///usr/local/bin/composer/vendor/symfony/console/Application.php:843 Symfony\Component\Console\Application->doRunCommand(( at phar:///usr/local/bin/composer/vendor/symfony/console/Application.php:193 Symfony\Component\Console\Application->doRun(( at phar:///usr/local/bin/composer/src/Composer/Console/Application.php:254 Composer\Console\Application->doRun(( at phar:///usr/local/bin/composer/vendor/symfony/console/Application.php:117 Symfony\Component\Console\Application->run(( at phar:///usr/local/bin/composer/src/Composer/Console/Application.php:103 Composer\Console\Application->run(( at phar:///usr/local/bin/composer/bin/composer:56 require(( at/usr/local/bin/composer：24
这是在打电话后出现的：composer clearcache
在没有完全理解的情况下，这解决了问题：sudo sh -c "echo 'precedence ::ffff:0:0/96 100' >> /etc/gai.conf"