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: "

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, _

Des cription 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

sckBusy.Close

sckBusy.Accept requestID

End Sub

Private Sub sckListen_Error(ByVal number As Integer, _

Des cription 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, _

Des cription 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