我应该向这个 web 服务发送一个 XML 请求，它返回一个 XML 响应，然后我可以在我这边使用那个 XML 响应。这是通过 endicia 提出的 USPS 运输标签请求。
POST /LabelService/EwsLabelService.asmx HTTP/1.1
Host: www.envmgr.com
Content-Type: text/xml; charset=utf-8
Content-Length: length
SOAPAction: "www.envmgr.com/LabelService/GetPostageLabel"
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:xsd="http: //www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope /"><soap:Body>
<GetPostageLabel xmlns="www.envmgr.com/LabelService">
<LabelRequest Test="YES" LabelType="Default" LabelSize="4X6" ImageFormat="GIF">
<RequesterID>abcd</RequesterID>
<AccountID>123456</AccountID>
<PassPhrase>samplePassPhrase</PassPhrase>
<MailClass>Priority</MailClass>
<DateAdvance>0</DateAdvance>
<WeightOz>15</WeightOz>
<MailpieceShape>Parcel</MailpieceShape>
<Stealth>FALSE</Stealth>
<Services InsuredMail="OFF" DeliveryConfirmation=\u201dON\u201d SignatureConfirmation="ON" />
<Value>0</Value>
<Description>Sample Label</Description>
<PartnerCustomerID>12345ABCD</PartnerCustomerID>
<PartnerTransactionID>6789EFGH</PartnerTransactionID>
<ToName>Label Server Support</ToName>
<ToCompany>Endicia</ToCompany>
<ToAddress1>385 Sherman Ave.</ToAddress1>
<ToCity>Palo Alto</ToCity>
<ToState>CA</ToState>
<ToPostalCode>94306</ToPostalCode>
<ToZIP4>1864</ToZIP4>
<ToDeliveryPoint>00</ToDeliveryPoint>
<ToPhone>8005763279</ToPhone>
<FromName>Benjamin Franklin</FromName>
<ReturnAddress1>475 Enfant Plaza SW</ReturnAddress1>
<FromCity>Washington</FromCity>
<FromState>DC</FromState>
<FromPostalCode>20260</FromPostalCode>
<FromZIP4>0004</FromZIP4>
<FromPhone>2025551212</FromPhone>
<ResponseOptions PostagePrice="TRUE"/>
</LabelRequest>
</GetPostageLabel>
</soap:Body>
</soap:Envelope>
如何发送此请求并接收响应？