Omeka has encountered an error

Apache_Solr_HttpTransportException

'0' Status: Communication Error

exception 'Apache_Solr_HttpTransportException' with message ''0' Status: Communication Error' in /var/www/omeka-2.3.1/plugins/SolrSearch/lib/solr-php-client/Service.php:338
Stack trace:
#0 /var/www/omeka-2.3.1/plugins/SolrSearch/lib/solr-php-client/Service.php(1176): Apache_Solr_Service->_sendRawGet('http://localhos...')
#1 /var/www/omeka-2.3.1/plugins/SolrSearch/controllers/ResultsController.php(168): Apache_Solr_Service->search('*:* AND collect...', 0, '100', Array)
#2 /var/www/omeka-2.3.1/plugins/SolrSearch/controllers/ResultsController.php(65): SolrSearch_ResultsController->_search(0, '100', true)
#3 /var/www/omeka-2.3.1/application/libraries/Zend/Controller/Action.php(516): SolrSearch_ResultsController->indexAction()
#4 /var/www/omeka-2.3.1/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('indexAction')
#5 /var/www/omeka-2.3.1/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#6 /var/www/omeka-2.3.1/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#7 /var/www/omeka-2.3.1/application/libraries/Zend/Application.php(382): Zend_Application_Bootstrap_Bootstrap->run()
#8 /var/www/omeka-2.3.1/application/libraries/Omeka/Application.php(79): Zend_Application->run()
#9 /var/www/omeka-2.3.1/index.php(23): Omeka_Application->run()
#10 {main}