冯 勇
Visual Basic6.0提供了Winsock控件，支持网络上两台计算机之间的通信。利用它，编程人员可以毫不费力地编写出TCP/IP客户/服务器程序。以下是用Visual Basic6.0的Winsock控件编写的网络聊天程序的实例。
一．客户程序的实现方法：
1．客户程序设置RemoteHost（远程主机）属性，指定运行服务器的主机名。
2．通过设置RemotePort属性，指定服务器程序的侦听端口。
3．客户程序使用Connect方法向服务器发送连接请求。
4．服务器若空闲，则接受客户的请求，客户程序发生Connect事件，然后可以用SendData方法发送数据。
5．客户程序收到数据时，产生DataArrival事件，在该事件中可以用GetData方法接收数据。
6．如果客户收到Close事件，用Close方法关闭连接。
以下是客户程序的编写过程：
1． 新建一个工程文件，在窗体中加上一个文本框Name为txtRecive，设置 MultiLine属性为True。设置ScrollBars属性为3-Both。
2． 加一标签，Caption为“您的大名：”，后面加一文本框Name为ClientName。
3． 加一标签，Caption为“您的性别：”，后面接一组合框Name为“xingbie“。组合框中加两个OptionButton，分别为Option1,Caption为“男”，Value为True,Option2,Caption为“女”。
4． 加文本框txtSent,设置MultiLine属性为True。
5． 加命令按钮cmdSent,Caption为“发送”， 再加一命令按钮cmdConnect，Caption为“连接”。
6． 加Winsock控件，Name为sckClient。
下面是客户程序的源代码：
Dim messIndex As Integer
Dim firsttime As Boolean
Dim recNumber As Integer
Dim strData As String
Private Sub cmdConnect_Click()
On Error GoTo MyError
sckClient.Connect
Exit Sub
MyError:
MsgBox "连接服务器出错！", vbOKOnly, "系统提示"
Exit Sub
End Sub
Private Sub cmdSent_Click()
Dim name As String
If txtSent.Text = "" Then
MsgBox "您想要说什么？", vbOKOnly, "系统提示"
Exit Sub
End If
If Option1.Value = True Then
name = clientname.Text + "先生: "
Else
name = clientname.Text + "小姐: "
End If
sckClient.SendData name + txtSent.Text
End Sub
Private Sub Form_Load()
sckClient.RemoteHost = "fdd" 注释：可以更改为你运行服务器的主机名
sckClient.RemotePort = 8888
cmdSent.Enabled = False
messIndex = -1
firsttime = True
recNumber = 0
End Sub
Private Sub sckClient_Close()
MsgBox "您使用的名字已经注册或服务器已关闭，请重新连接。"
End
End Sub
Private Sub sckClient_Connect()
Dim name As String
MsgBox "连接服务器成功！", vbOKOnly, "系统提示"
cmdConnect.Enabled = False
cmdSent.Enabled = True
If firsttime = True Then
If Option1.Value = True Then
name = clientname.Text + "先生"
Else
name = clientname.Text + "小姐"
End If
sckClient.SendData name
firsttime = False
End If
clientname.Enabled = False
If Option1.Value = True Then
Option2.Enabled = False
Option1.Enabled = False
Else
Option1.Enabled = False
Option2.Enabled = False
End If
End Sub
Private Sub sckClient_DataArrival(ByVal bytesTotal As Long)
sckClient.GetData strData
txtRecive.Text = txtRecive.Text & strData & vbCrLf
txtRecive.SelStart = Len(txtRecive.Text)
End Sub
Private Sub sckClient_Error(ByVal Number As Integer, _
Description As String, ByVal Scode As Long, _
ByVal Source As String, ByVal HelpFile As String, _
ByVal HelpContext As Long, CancelDisplay As Boolean)
sckClient.Close
cmdConnect.Enabled = True
cmdSent.Enabled = False
End Sub
二．服务器程序的实现方法：
1． 设置LocalPort属性，作为侦听端口。该值是一个整型值，但必须是其他TCP/IP程序没有使用过的值。
2． 使用Listen方法进入侦听状态，等待客户程序发出连接请求。
3． 收到客户的连接请求，服务器发生ConnectRequest事件，得到RequestID。
4． 服务器程序用Accept方法接受客户的连接请求。然后可以用SendData方法发送数据。
5． 服务器接受到数据时，发生DataArrival事件，在该事件中可以用GetData的方法接收数据。
6． 如果接收到Close事件，则用Close方法关闭TCP/IP连接。
以下是服务器程序的编写过程：
1． 新建一个工程文件，在窗体中加上一个文本框Name为txtRecive，设置 MultiLine属性为True。设置ScrollBars属性为3-Both。
2． 加一标签，Caption为“连接数”，后面接一个标签，Name为number,Caption为0，设置Appearance为1-3D，BorderStyle为1-Fixed Single。
3． 加一命令按钮，Name为clearmess,Caption为“清除消息”。
4． 加三个WinSock控件，Name分别为sckServer,sckBusy,sckListen。
下面是服务器程序的源代码：
Private MaxNumber As Integer
Dim curnumber As Integer
Dim chatname(50) As String
Dim firstmess(50) As Boolean
Private Sub clearmess_Click()
txtRecive.Text = ""
End Sub
Private Sub Form_Load()
MaxNumber = 50
curnumber = 0
For l = 0 To MaxNumber
firstmess(l) = True
Next l
For i = 1 To MaxNumber - 1
Load sckServer(i)
Next i
sckListen.LocalPort = 8888
sckListen.Listen
End Sub
Private Sub sckBusy_Close()
sckBusy.Close
End Sub
Private Sub sckBusy_DataArrival(ByVal bytesTotal As Long)
sckBusy.SendData "服务器忙，请稍后再连接！"
DoEvents
End Sub
Private Sub sckListen_ConnectionRequest(ByVal requestID As Long)
Dim i As Integer
For i = 0 To MaxNumber - 1
If sckServer(i).State = 0 Then
Exit For
End If
Next i
If sckServer(i).State = 0 Then
sckServer(i).Accept requestID
sckServer(i).SendData "欢迎您参加入网络聊天！"
curnumber = curnumber + 1
number.Caption = curnumber
Exit Sub
End If
sckBusy.Close
sckBusy.Accept requestID
End Sub
Private Sub sckListen_Error(ByVal number As Integer, _
Description As String, ByVal Scode As Long, _
ByVal Source As String, ByVal HelpFile As String, _
ByVal HelpContext As Long, CancelDisplay As Boolean)
sckListen.Close
sckListen.LocalPort = 8888
sckListen.Listen
End Sub
Private Sub sckServer_Close(Index As Integer)
Dim j As Integer
sckServer(Index).Close
firstmess(Index) = True
For j = 0 To MaxNumber - 1
If sckServer(j).State = 7 Then
sckServer(j).SendData chatname(Index) + "退出网络聊天"
DoEvents
End If
Next j
curnumber = curnumber - 1
number.Caption = curnumber
End Sub
Private Sub sckServer_DataArrival(Index As Integer, ByVal bytesTotal As Long)
Dim strData As String
Dim i As Integer
sckServer(Index).GetData strData
If firstmess(Index) = True Then
chatname(Index) = strData
firstmess(Index) = False
For m = 0 To 49
If (Index <> m) And (chatname(m) = strData) Then
sckServer(Index).Close
firstmess(Index) = True
curnumber = curnumber - 1
number.Caption = curnumber
Exit Sub
End If
Next m
strData = strData + "加入网络聊天"
End If
For i = 0 To MaxNumber - 1
If sckServer(i).State = 7 Then
sckServer(i).SendData strData
DoEvents
End If
Next i
txtRecive.Text = txtRecive.Text & "Index " & Index & " " & strData + vbCrLf
txtRecive.SelStart = Len(txtRecive.Text)
End Sub
Private Sub sckServer_Error(Index As Integer, ByVal number As Integer, _
Description As String, ByVal Scode As Long, ByVal Source As String, _
ByVal HelpFile As String, ByVal HelpContext As Long, _
CancelDisplay As Boolean)
sckServer(Index).Close
End Sub
