Source

File: wp-admin/includes/class-wp-site-health.php

public function get_test_http_requests() {
		$result = array(
			'label'       => __( 'HTTP requests seem to be working as expected' ),
			'status'      => 'good',
			'badge'       => array(
				'label' => __( 'Performance' ),
				'color' => 'blue',
			),
			'description' => sprintf(
				'<p>%s</p>',
				__( 'It is possible for site maintainers to block all, or some, communication to other sites and services. If set up incorrectly, this may prevent plugins and themes from working as intended.' )
			),
			'actions'     => '',
			'test'        => 'http_requests',
		);

		$blocked = false;
		$hosts   = array();

		if ( defined( 'WP_HTTP_BLOCK_EXTERNAL' ) && WP_HTTP_BLOCK_EXTERNAL ) {
			$blocked = true;
		}

		if ( defined( 'WP_ACCESSIBLE_HOSTS' ) ) {
			$hosts = explode( ',', WP_ACCESSIBLE_HOSTS );
		}

		if ( $blocked && 0 === sizeof( $hosts ) ) {
			$result['status'] = 'critical';

			$result['label'] = __( 'HTTP requests are blocked' );

			$result['description'] .= sprintf(
				'<p>%s</p>',
				sprintf(
					/* translators: %s: Name of the constant used. */
					__( 'HTTP requests have been blocked by the %s constant, with no allowed hosts.' ),
					'<code>WP_HTTP_BLOCK_EXTERNAL</code>'
				)
			);
		}

		if ( $blocked && 0 < sizeof( $hosts ) ) {
			$result['status'] = 'recommended';

			$result['label'] = __( 'HTTP requests are partially blocked' );

			$result['description'] .= sprintf(
				'<p>%s</p>',
				sprintf(
					/* translators: 1: Name of the constant used. 2: List of allowed hostnames. */
					__( 'HTTP requests have been blocked by the %1$s constant, with some allowed hosts: %2$s.' ),
					'<code>WP_HTTP_BLOCK_EXTERNAL</code>',
					implode( ',', $hosts )
				)
			);
		}

		return $result;
	}