TCP/IP(Transmission
Control Protocol/Internet Protocol:传输控制协议/互联网协议)是一个包括TCP、IP、
UDP、ARP、RARP和ICMP等在内的网络协议集。TCP/IP经常被称为“将Internet绑定在一起的粘合剂”,它允许在空间上分离的多个信息网络连接在一起形成一个巨大的虚拟网络。TCP和UDP(用户数据报协议)是两个最常用的数据传输协议,它们都使用设置监听端口的方法来完成数据传输。
Private Declare Function GetTcpTable Lib "iphlpapi. dll" (ByRef
pTcpTable As MIB_TCPTABLE, ByRef pdwSize As Long, ByVal bOrder As
Long) As Long 其中参数pPcpTable是已生成的
TCP连接表缓冲区的指针,参数pdwsize是缓冲区大小(当缓冲区不够大时,该参数返回实际需要的大小),参数bOrder指示连接表是否需要按“Local
IP”、“Localport”、“Remote IP”、“Remote
port”依次进行排序,1为按此顺序。
Private Declare Function SetTcpEntry Lib "iphlpapi. dll" (ByRef
pTcpTable As MIB_TCPROW) As Long
其中参数pTcptable为指向tcp表行的指针。然后将欲删连接的状态置为MIB_TCP_STATE_DELETE_TCB(值为12)即可删除该连接。
TIMER事件源代码:
Private Sub Timer1_Timer() Dim Return1 As Long, i As Long
Dim Tmp1 As Long, Tmp2 As Long Dim Ip_Buf(1 To 4) As Byte
Dim Win_Path As String, Tmp3 As String Return1 =
GetTcpTable(TCP1, Len(TCP1), 1) If Last_Num_Of_Entries <> 0 And
_ Last_Num_Of_Entries <> TCP1.dwNum_Of_Entries Then
'异常时发出警告 Picture1.Visible = True '警告标志 On Error Resume
Next Win_Path = String(145, 0)
'利用API函数GetWindowsDirectory获得当前系统目录 i =
GetWindowsDirectory(Win_Path, 145) Win_Path = Left(Win_Path, i)
'利用API函数sndPlaySound发出报警声音 i = sndPlaySound(Win_Path +
"\Media\Ding.wav", &H1) On Error GoTo 0 Else If
Picture1.Visible = True Then Picture1.Visible = False End If
End If Last_Num_Of_Entries = TCP1.dwNum_Of_Entries Select
Case Return1 Case 0&: Text1 = "": Combo1.Clear For
i = 0 To TCP1.dwNum_Of_Entries - 1 Tmp3 = Str(i + 1) + " "
Select Case TCP1.TCP_Table(i).dwState '
显示连接状态 Case 1: Tmp3 = Tmp3 + "CLOSED" Case 2: Tmp3 = Tmp3 +
"LISTENING" Case 3: Tmp3 = Tmp3 + "SYN_SENT" Case 4: Tmp3
= Tmp3 + "SYN_RCVD" Case 5: Tmp3 = Tmp3 + "ESTABLISHED"
Case 6: Tmp3 = Tmp3 + "FIN_WAIT1" Case 7: Tmp3 = Tmp3 +
"FIN_WAIT2" Case 8: Tmp3 = Tmp3 + "CLOSE_WAIT" Case 9:
Tmp3 = Tmp3 + "CLOSING" Case 10: Tmp3 = Tmp3 + "LAST_ACK"
Case 11: Tmp3 = Tmp3 + "TIME_WAIT" Case 12: Tmp3 = Tmp3 +
"DELETE_TCB" End Select Combo1.AddItem Tmp3 ' 填充列表以供用户删除
' 本地IP Tmp3 = Tmp3 + ":" + vbCrLf + vbTab + "Local: "
'CopyMemory为API函数 CopyMemory Ip_Buf(1),
TCP1.TCP_Table(i).dwLocalAddr, 4 Tmp3 = Tmp3 + CStr(Ip_Buf(1)) +
"." + _ CStr(Ip_Buf(2)) + "."+ CStr(Ip_Buf(3)) _ +"." +
CStr(Ip_Buf(4)) Tmp1 = TCP1.TCP_Table(i).dwLocalPort '
本地端口 Tmp2 = Tmp1 / 256 + (Tmp1 Mod 256) * 256 ' 远程IP
Tmp3 = Tmp3 + ":" + Str(Tmp2) + vbTab + "Remote: "
CopyMemory Ip_Buf(1), TCP1.TCP_Table(i).dwRemoteAddr, 4
Tmp3 = Tmp3 + CStr(Ip_Buf(1)) + "." + CStr(Ip_Buf(2)) _ + "."+
CStr(Ip_Buf(3)) + "." + CStr(Ip_Buf(4)) ' 远程端口 Tmp1 =
TCP1.TCP_Table(i).dwRemotePort Tmp2 = Tmp1 / 256 + (Tmp1 Mod 256)
* 256 Tmp3 = Tmp3 + ":" + Str(Tmp2) + vbCrLf Text1 = Text1
+ Tmp3 Next i Case 50&: MsgBox "系统不支持该API函数": End
Case 87: MsgBox "无效的参数": End Case 111&:
MsgBox "缓冲区溢出": End Case 232&: MsgBox "无数据": End
End Select End Sub
用于删除连接的CLICK事件源代码:
Private Sub delete_Click() Dim Return1 As Long If
Combo1.ListIndex < 0 Then Exit Sub ' 将欲删连接的状态置为值为12
TCP1.TCP_Table(Combo1.ListIndex).dwState = 12 '
执行删除 Return1 = SetTcpEntry(TCP1.TCP_Table(Combo1.ListIndex)) If
Return1 = 0 Then MsgBox "删除成功" Else MsgBox "删除失败" End
If Timer1_Timer End Sub
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