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POc++ to vb.net , problems with callback function
 

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    <p>I'm having a hard time here trying to find a solution for my problem.</p> <p>I'm trying to convert a client API funktion from C++ to VB.NET, and i think have some problems with the callback function.</p> <p>parts of the C++ code:</p> <p>typedef struct{</p> <pre><code>BYTE m_bRemoteChannel; BYTE m_bSendMode; BYTE m_nImgFormat; // =0 cif ; = 1 qcif char *m_sIPAddress; char *m_sUserName; char *m_sUserPassword; BOOL m_bUserCheck; HWND m_hShowVideo; </code></pre> <p>}CLIENT_VIDEOINFO, *PCLIENT_VIDEOINFO;</p> <p>CPLAYER_API LONG __stdcall MP4_ClientStart(PCLIENT_VIDEOINFO pClientinfo,void(CALLBACK *ReadDataCallBack)(DWORD nPort,UCHAR *pPacketBuffer,DWORD nPacketSize));</p> <p>void CALLBACK ReadDataCallBack(DWORD nPort,UCHAR *pPacketBuffer,DWORD nPacketSize)</p> <p>{ TRACE("%d\n",nPacketSize); }</p> <pre><code> ..... aa5.m_sUserName = "123"; aa5.m_sUserPassword="w"; aa5.m_bUserCheck = TRUE; MP4_ClientSetTTL(64); nn1 = MP4_ClientStart(&amp;aa5,ReadDataCallBack); if (nn1 == -1) { MessageBox("error"); return; } </code></pre> <hr> <p>SDK description:</p> <ol start="3"> <li>MP4_ClientStart</li> </ol> <p>This function starts a connection. The format of the call is:</p> <p>LONG __stdcall MP4_ClientStart(PCLIENT_VIDEOINFO pClientinfo, void(*ReadDataCallBack)(DWORD nChannel,UCHAR *pPacketBuffer,DWORD nPacketSize))</p> <p>Parameters pClientinfo holds the information. of this connection.</p> <p>nChannel holds the channel of card.</p> <p>pPacketBuffer holds the pointer to the receive buffer.</p> <p>nPacketSize holds the length of the receive buffer.</p> <p>Return Values If the function succeeds the return value is the context of this connection. If the function fails the return value is -1.</p> <p>Remarks</p> <p>typedef struct{</p> <p>BYTE m_bRemoteChannel;</p> <p>BYTE m_bSendMode;</p> <p>BYTE m_bImgFormat;</p> <p>char *m_sIPAddress;</p> <p>char *m_sUserName;</p> <p>char *m_sUserPassword;</p> <p>BOOL m_bUserCheck;</p> <p>HWND m_hShowVideo;</p> <p>} CLIENT_VIDEOINFO, * PCLIENT_VIDEOINFO;</p> <p>m_bRemoteChannel holds the channel which the client wants to connect to.</p> <p>m_bSendMode holds the network mode of the connection.</p> <p>m_bImgFormat : Image format, 0 is main channel video, 1 is sub channel video</p> <p>m_sIPAddress holds the IP address of the server.</p> <p>m_sUserName holds the user’s name.</p> <p>m_sUserPassword holds the user’s password.</p> <p>m_bUserCheck holds the value whether sends the user’s name and password or not.</p> <p>m_hShowVideo holds Handle for this video window.</p> <p>If m_hShowVideo holds NULL, the client can be record only without decoder.</p> <p>If m_bUserCheck is FALSE, we will send m_sUserName and m_sUserPassword as NULL, else we will send each 50 bytes.</p> <p>The length of m_sIPAddress and m_sUserName must be more than 50 bytes.</p> <p>ReadDataCallBack: When the library receives a packet from a server, this callback is called.</p> <hr> <p>My VB.Net code:</p> <p>Imports System.Runtime.InteropServices</p> <p>Public Class Form1</p> <pre><code>Const WM_USER = &amp;H400 Public Structure CLIENT_VIDEOINFO Public m_bRemoteChannel As Byte Public m_bSendMode As Byte Public m_bImgFormat As Byte Public m_sIPAddress As String Public m_sUserName As String Public m_sUserPassword As String Public m_bUserCheck As Boolean Public m_hShowVideo As Long 'hWnd End Structure Public Declare Function MP4_ClientSetNetPort Lib "hikclient.dll" (ByVal dServerPort As Integer, ByVal dClientPort As Integer) As Boolean Public Declare Function MP4_ClientStartup Lib "hikclient.dll" (ByVal nMessage As UInteger, ByVal hWnd As System.IntPtr) As Boolean &lt;DllImport("hikclient.dll")&gt; Public Shared Function MP4_ClientStart(ByVal Clientinfo As CLIENT_VIDEOINFO, ByRef ReadDataCallBack As CALLBACKdel) As Long End Function Public Delegate Sub CALLBACKdel(ByVal nPort As Long, &lt;MarshalAs(UnmanagedType.LPArray)&gt; ByRef pPacketBuffer As Byte(), ByVal nPacketSize As Long) Public Sub CALLBACK(ByVal nPort As Long, &lt;MarshalAs(UnmanagedType.LPArray)&gt; ByRef pPacketBuffer As Byte(), ByVal nPacketSize As Long) End Sub Public mydel As New CALLBACKdel(AddressOf CALLBACK) Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim Clientinfo As New CLIENT_VIDEOINFO() Clientinfo.m_bRemoteChannel = 0 Clientinfo.m_bSendMode = 0 Clientinfo.m_bImgFormat = 0 Clientinfo.m_sIPAddress = "193.168.1.100" Clientinfo.m_sUserName = "1" Clientinfo.m_sUserPassword = "a" Clientinfo.m_bUserCheck = False Clientinfo.m_hShowVideo = Me.Handle 'Nothing MP4_ClientSetNetPort(850, 850) MP4_ClientStartup(WM_USER + 1, Me.Handle) MP4_ClientStart(Clientinfo, mydel) End Sub </code></pre> <p>End Class</p> <hr> <p>here is some other examples of the code in:</p> <p>C#</p> <p><a href="http://blog.csdn.net/nenith1981/archive/2007/09/17/1787692.aspx" rel="nofollow noreferrer">http://blog.csdn.net/nenith1981/archive/2007/09/17/1787692.aspx</a></p> <p>VB</p> <p>://read.pudn.com/downloads70/sourcecode/graph/250633/MD%E5%AE%A2%E6%88%B7%E7%AB%AF%28VB%29/hikclient.bas__.htm</p> <p>://read.pudn.com/downloads70/sourcecode/graph/250633/MD%E5%AE%A2%E6%88%B7%E7%AB%AF%28VB%29/Form1.frm__.htm</p> <p>Delphi</p> <p>://read.pudn.com/downloads91/sourcecode/multimedia/streaming/349759/Delphi_client/Unit1.pas__.htm</p>
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    2. COI getting a error on: MP4_ClientStart(Clientinfo, mydel) .................... Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. The thread 0x1f9c has exited with code 0 (0x0). The program '[6796] temp.vshost.exe: Managed' has exited with code -1073741819 (0xc0000005).
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