编写网络寻呼机
1、在VB中编写网络寻呼机需要建立两个程序，一个为客户端程序Client，一个为服务器端程序Server。
一、在Client工程中建立一个窗体，加载WinSock控件，称为tcpClient，协议选择TCP。再加入四个文本框，用以输入服务器的IP地址、服务器端口号，被呼叫的网络寻呼ID号以及用户登录ID号。然后再在窗体中加入三个按钮，分别命名为“连接”、“断开”和“退出”，点击“连接”按钮，并进行如下初始化连接，代码如下：
2、Private Sub Command1_Click()
If Len(Text1.Text) = 0 And Len(Text2.Text) = 0 Then
MsgBox ("请输入主机名或主机IP地址。")
Exit Sub
ElseIf Len(Text1.Text) > 0 Then
tcpClient.RemoteHost = Text1.Text
tcpClient.RemotePort = Text2.Text
End If
tcpClient.Connect
Timer1.Enabled = True
End Sub
Private Sub Command2_Click()
tcpClient.Close '断开连接
End Sub
Private Sub Command3_Click()
End
End Sub
Private Sub Form_Load()
Text2.Text = "1001"
End Sub
Private Sub tcpClient_Connect()
tcpClient.SendData (Text3.Text&"@"&Text4.Text)
End Sub
Private Sub tcpClient_DataArrival(ByVal bytesTotal As Long)
Dim strData As String
tcpClient.GetData strData
strData = strData + "呼叫"
'在收到呼叫消息后弹出一对话框并显示主叫方ID号码
MsgBox (strData)
End Sub
3、二、在服务器端Server工程中也建立一个窗体，加载WinSock控件，称为tcpServer，协议选择TCP，设置其Index值为0，并在工程中添加模块。内容如下：
Private Type ActiveUser
ClientIP As String '记录客户的IP地址
ClientPort As Integer '记录当前会话的端口
ClientID As Long '记录客户的ID号码
ClientConnected As Boolean '客户连接状态，True表示已连接，False表示没有连接
End Type
Dim CurUser() As ActiveUser
Dim tcpIndex As Integer '跟踪当前建立连接数
4、在Form_Load事件中加入如下代码：
Private Sub Form_Load()
tcpServer(0).Protocol = sckTCPProtocol
tcpServer(0).LocalPort = 1001
'将 LocalPort 属性设置为一个整数。
tcpServer(0).Listen '然后调用 Listen 方法。
tcpIndex = 1
End Sub
5、准备应答客户端程序的请求连接，使用ConnectionRequest事件来应答户端程序的请求，代码如下：
Private Sub tcpServer_ConnectionRequest(Index As Integer, ByVal requestID As Long)
Dim i As Integer
On Error GoTo ErrHandle
For i = 1 To tcpIndex '选择一个空闲端口
If CurUser(i).ClientConnected = False And i < > tcpIndex Then
Load tcpServer(i)
tcpServer(i).LocalPort = CurUser(i).ClientPort - 1
tcpServer(i).Accept requestID
Exit For
ElseIf CurUser(i).ClientConnected = False Then
Load tcpServer(i)
tcpServer(i).LocalPort = Port
If tcpServer(i).State < > sckClosed Then
tcpServer(i).Close
End If
tcpServer(i).Accept requestID
Exit For
End If
Next
DoEvents
6、'测试连接是否成功
If tcpServer(i).State = sckConnected Then
If i = tcpIndex Then
'已经没有可用端口,记录客户的IP地址和端口号
tcpIndex = tcpIndex + 1
Port = Port + 1
ReDim Preserve CurUser(tcpIndex)
CurUser(i).ClientIP = tcpServer(i).RemoteHostIP
CurUser(i).ClientConnected = True
CurUser(i).ClientPort = Port
CurUser(tcpIndex).ClientConnected = False
Else
CurUser(i).ClientIP = tcpServer(i).RemoteHostIP
CurUser(i).ClientPort = Port
CurUser(i).ClientConnected = True
End If
End If
Exit Sub
ErrHandle:
Resume Next
7、 '检查控件的 State 属性,如未关闭，在接受新的连接之前关闭此连接。
If tcpServer(0).State <> sckClosed Then
tcpServer(0).Close
tcpServer(0).Accept requestID
'接受具有 requestID 参数的,连接。
End Sub
Private Sub tcpServer_DataArrival(Index As Integer, ByVal bytesTotal As Long)
Dim i As Integer
Dim s As String
Dim RequID As Long '主叫方ID号码
Dim SearchID As Long '被叫方ID号码
On Error GoTo ErrHandle
tcpServer(Index).GetData s, vbString
'接收数据并存入s
If Mid(s, i, 1) = "@" Then
'分离s中的主叫方和被叫方ID号码
SearhID = Left(s, i - 1) '把号存入mKey
RequID = Right(s, Len(s) - i) 'ID存入RequID
End If
'如果是请求寻呼某一ID号码,则检索当前此ID用户是否登录（即CurUser数组中是否存在此用户）,然后发送信息，通知此用户响应呼叫并显示主叫用户ID号码。
For i = 1 To tcpIndex
If RequID = CurUser(i).ClientID And CurUser(i).ClientConnected = True Then
tcpServer(i).SendData (SearhID)
End If
Next
Exit Sub
ErrHandle:
If Err.Number = sckBadState Then '连接不正确
CurUser(i).ClientConnected = False
CurUser(i).ClientIP = ""
Unload tcpServer(i)
Resume Next
End If
End Sub
