PHP致命错误：未捕获的SoapFault异常：[HTTP]无法连接到主机

我有一个PHP SOAP服务器，它作为SOAP客户端与另一个SOAP服务器通信。我用过nusoap图书馆

当通信量较低时，SOAP服务器工作正常。但当服务器请求被激怒时，我们收到了一些请求的错误

PHP Fatal error:  Uncaught SoapFault exception: [HTTP] Could not connect to host in /home/public_html/api/soapserver.php:

Stack trace:
0 [internal function]: SoapClient->__doRequest('<?xml version="...', 'http://100.20.5...', 'urn:NameSpc#Fin...', 1, 0)

1 /home/public_html/api/soapserver.php (103): SoapClient->__soapCall('FindClient...', Array)

2 [internal function]: FindClientInfo('username', 'password')

3 /home/public_html/api/lib/nusoap.php(4206): call_user_func_array('FindClient...', Array)

4 /home/public_html/api/lib/nusoap.php(3828): nusoap_server->invoke_method()

5 /home/public_html/api/soapserver.php(25): nusoap_server->service('<?xml version="...')

6 {main}

PHP致命错误：未捕获的SoapFault异常：[HTTP]无法连接到/home/public\u html/api/soapserver.PHP中的主机：
堆栈跟踪：
0[内部函数]：SoapClient->\uuu doRequest（'