我相信您唯一的问题是Web服务器的配置。每个Web服务的配置（在我的例子中是web.config文件，因为我使用的是IIS）应该允许管理允许访问它的协议：获取、发布和/或Soap。
我刚刚测试了我自己的Web服务，它对来自我的浏览器的GET请求做出了响应......它还对POST请求做出了预期的响应（我将https://web.archive.org/web/20210619192654/https://www.4guysfromrolla.com/articles/022410-1.aspx中的一些代码改编为以下代码片段：）

Dim payload As Byte()
    payload = Text.Encoding.ASCII.GetBytes("paramName=firstValue&p2=secondValue")

    Dim webRequest As System.Net.HttpWebRequest
    webRequest = System.Net.HttpWebRequest.Create("http://www.servername.com/DataService.asmx/GetVersion")
    webRequest.Method = "POST"
    webRequest.KeepAlive = False
    webRequest.ContentType = "application/x-www-form-urlencoded"
    webRequest.ContentLength = payload.Length

    Dim reqStream As System.IO.Stream
    reqStream = webRequest.GetRequestStream()
    reqStream.Write(payload, 0, payload.Length)
    reqStream.Close()

    Dim webResponse As System.Net.HttpWebResponse
    webResponse = webRequest.GetResponse()

    Dim reader As System.IO.StreamReader
    reader = New System.IO.StreamReader(webResponse.GetResponseStream())
    Dim xmlDoc As System.Xml.XmlDocument
    xmlDoc = New System.Xml.XmlDocument()
    xmlDoc.LoadXml(reader.ReadToEnd())

祝你好运