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Asked: 2026-06-17T22:03:37+00:00

I connected successfully to onlinenic API using TCP client, but facing an error when

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I connected successfully to onlinenic API using TCP client, but facing an error when trying to login.

Below is my code (Username and password are demo as was provided by onlinenic)

    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

when i try to connect using the above login() function I got the following error :

Object reference not set to an instance of an object.

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)

The error message am getting on this line : stream.Write(data, 0, data.Length)

System.NullReferenceException was unhandled by user code
Message=Object reference not set to an instance of an object.
Source=App_Web_4023pkvf StackTrace:
at _Default.Login() in D:\Documents and Settings\sa\My Documents\Visual Studio
2010\WebSites\onlinenic_vb1\Default.aspx.vb:line 51
at _Default.Button2_Click(Object sender, EventArgs e) in D:\Documents and Settings\sa\My Documents\Visual Studio
2010\WebSites\onlinenic_vb1\Default.aspx.vb:line 243
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String
eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException:

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1 Answer

  1. Editorial Team

    You should try this :

     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")
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