onvif 相机 在线判断 发送的Probe信息有误？

Question

我想向一个相机发送Hello消息，通过相机有无回应来判断该相机是否在线。
一下是我的代码，
wsddProxy oProxy("http://192.168.6.54/onvif/device_service");
oProxy.recv_timeout = 2;
oProxy.header = soap_new_SOAP_ENV__Header(&oProxy);
soap_default_SOAP_ENV__Header(&oProxy, oProxy.header);
oProxy.header->wsa__RelatesTo=0;
oProxy.header->wsa__From = 0;

oProxy.header->wsa__ReplyTo = 0;
oProxy.header->wsa__FaultTo = 0;
oProxy.header->wsdd__AppSequence = 0;
oProxy.header->wsa__MessageID = (char*)soap_malloc(&oProxy, 256 );
oProxy.header->wsa__To = (char*)soap_malloc(&oProxy, 256 );
oProxy.header->wsa__Action = (char*)soap_malloc(&oProxy, 256 );

strcpy_s(oProxy.header->wsa__Action,  250 , "http://schemas.xmlsoap.org/ws/2005/04/discovery/Probe");
strcpy_s(oProxy.header->wsa__To, 250 , "urn:schemas-xmlsoap-org:ws:2005:04:discovery");
strcpy_s(oProxy.header->wsa__MessageID, 250 ,  "uuid:" + GlobalFunction::CreateGUID());

wsdd__ProbeType oSendParam;
soap_default_wsdd__ProbeType(&oProxy, &oSendParam);
//oSendParam.Types = "tdn:NetworkVideoTransmitter";
oSendParam.Types = "tdn:Device";
__wsdd__ProbeMatches oReceiveParam;
soap_default___wsdd__ProbeMatches(&oProxy, &oReceiveParam);
oProxy.Probe(&oSendParam);

int n = oProxy.recv_ProbeMatches(oReceiveParam);
if (SOAP_OK == n) // 接收到Device反馈
{
}

n的返回值总是-1，是我的soap_endpoint错误，还是什么问题。对Onvif了解的很少，文档看的不是很懂，求帮助！