通过 TCP (VB.NET) 发送字符串答案

【问题标题】：send string through TCP (VB.NET)通过 TCP (VB.NET) 发送字符串
【发布时间】：2013-03-11 22:39:42
【问题描述】：

我使用 TCP 客户端成功连接到 onlinenic API，但在尝试登录时遇到错误。

下面是我的代码（用户名和密码是由 onlinenic 提供的演示）

    Imports System
    Imports System.Net.Sockets
    Imports System.Text
Imports System.Security.Cryptography
Imports System.IO
Imports System.Text.RegularExpressions
Imports System.Configuration
Imports System.Xml.Linq
Imports System.Xml

Partial Public Class _Default
    Inherits System.Web.UI.Page
    Private client As New TcpClient()
    Private stream As NetworkStream
    Private PortNo As Integer = 30009
    Private testIP As String = "218.5.81.149"
    Private testID As String = "135610"
    Private testPassword As String = "654123"
    Private Function Connect() As Boolean
        client.Connect(testIP, PortNo)
        stream = client.GetStream()
        Dim responseData As String = ""
        Dim data As [Byte]() = New [Byte](255) {}
        Dim bytes As Int32 = stream.Read(data, 0, data.Length)
        responseData = Encoding.ASCII.GetString(data, 0, bytes)
        Return responseData.Contains("Your Connection with API Server is Successful")
    End Function




    Private Function Login() As Boolean
        Dim HashedPass As String = CreateMd5Hash(testPassword)
        Dim guid__1 As Guid = Guid.NewGuid()
        Dim chksum As String = CreateMd5Hash(testID + HashedPass + guid__1.ToString() + "login")
        Dim sb As New StringBuilder()
        sb.Append("<?xml version=""1.0"" encoding=""UTF-8"" standalone=""no""?>")
        sb.Append("<request>")
        sb.Append("<category>client</category>")
        sb.Append("<action>Login</action>")
        sb.Append("<params>")
        sb.Append("<param name=""clid"">" + testID + "</param>")
        sb.Append("</params>")
        sb.Append("<cltrid>" + guid__1.ToString() + "</cltrid>")
        sb.Append("<chksum>" + chksum + "</chksum>")
        sb.Append("</request>")
        Dim responseData As [String] = [String].Empty
        Dim data As [Byte]()
        data = System.Text.Encoding.ASCII.GetBytes(sb.ToString())
        stream.Write(data, 0, data.Length)
        Dim bytes As Int32 = stream.Read(data, 0, data.Length)
        responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes)
        bytes = stream.Read(data, 0, data.Length)
        responseData += System.Text.Encoding.ASCII.GetString(data, 0, bytes)
        Return responseData.Contains("Command completed successfully")
    End Function

当我尝试使用上述 login() 函数连接时，出现以下错误：

对象引用未设置为对象的实例。

Line 49:         Dim data As [Byte]()
Line 50:         data = System.Text.Encoding.ASCII.GetBytes(sb.ToString())
Line 51:         stream.Write(data, 0, data.Length)
Line 52:         Dim bytes As Int32 = stream.Read(data, 0, data.Length)
Line 53:         responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes)

错误信息出现在这一行：stream.Write(data, 0, data.Length)

System.NullReferenceException 未被用户代码处理
Message=对象引用未设置为对象的实例。
来源=App_Web_4023pkvf StackTrace：在 D:\Documents and Settings\sa\My Documents\Visual Studio 中的 _Default.Login() 2010\WebSites\onlinenic_vb1\Default.aspx.vb: 第 51 行在 D:\Documents and Settings\sa\My Documents\Visual Studio 中的 _Default.Button2_Click(Object sender, EventArgs e) 2010\WebSites\onlinenic_vb1\Default.aspx.vb:243 行在 System.Web.UI.WebControls.Button.OnClick（EventArgs e）在 System.Web.UI.WebControls.Button.RaisePostBackEvent（字符串 eventArgument）在 System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent（字符串事件参数）在 System.Web.UI.Page.RaisePostBackEvent（IPostBackEventHandler sourceControl，字符串 eventArgument）在 System.Web.UI.Page.RaisePostBackEvent（NameValueCollection postData）在 System.Web.UI.Page.ProcessRequestMain（布尔 includeStagesBeforeAsyncPoint，布尔 includeStagesAfterAsyncPoint）
内部异常：

【问题讨论】：

在哪一行抛出异常？
第 51 行：stream.Write(data, 0, data.Length)
供参考的API是：onlinenic.com/cp_english/template_api/download/…
看起来“流”此时为空。你在 Login() 之前运行 Connect() 吗？
是的，我使用 connect() 成功连接，然后尝试 login()。我从其他 C# 代码转换了这段代码。

标签： vb.net tcpclient

【解决方案1】：

你应该试试这个：

 Dim HashedPass As String = CreateMd5Hash(testPassword)
        Dim guid__1 As Guid = Guid.NewGuid()
        Dim chksum As String = CreateMd5Hash(testID + HashedPass + guid__1.ToString() + "login")
        Dim sb As New StringBuilder()
        sb.Append("<?xml version=""1.0"" encoding=""UTF-8"" standalone=""no""?>")
        sb.Append("<request>")
        sb.Append("<category>client</category>")
        sb.Append("<action>Login</action>")
        sb.Append("<params>")
        sb.Append("<param name=""clid"">" + testID + "</param>")
        sb.Append("</params>")
        sb.Append("<cltrid>" + guid__1.ToString() + "</cltrid>")
        sb.Append("<chksum>" + chksum + "</chksum>")
        sb.Append("</request>")
        Dim responseData As [String] = [String].Empty
        Dim data As [Byte]()
        data = System.Text.Encoding.ASCII.GetBytes(sb.ToString())
        stream.Write(data, 0, data.Length)
        Dim bytes As Int32 = stream.Read(data, 0, data.Length)
        responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes)
        bytes = stream.Read(data, 0, data.Length)
        responseData += System.Text.Encoding.ASCII.GetString(data, 0, bytes)
        Return responseData.Contains("Command completed successfully")

【讨论】：