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用 vb.net socket通信
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Dim th As Threading.Thread
2 Dim tcpl As System.Net.Sockets.TcpListener
3
4 Private Sub Form1_Load()Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
5 th = New System.Threading.Thread(New System.Threading.ThreadStart(AddressOf MyListen))
6 th.Start()
7 End Sub
8
9 Public Sub SendMessage()Sub SendMessage(ByVal IP As String, ByVal SendMsg As String)
10 Try
11 If IP "" Then
12 Dim tcpc As New System.Net.Sockets.TcpClient(IP, 5656)
13 Dim tcpStream As Net.Sockets.NetworkStream = tcpc.GetStream
14 Dim reqStream As New IO.StreamWriter(tcpStream)
15 reqStream.Write(SendMsg)
16 reqStream.Flush()
17 tcpStream.Close()
18 tcpc.Close()
19 End If
20 Catch ex As Exception
21 MsgBox(ex.Message.ToString)
22 End Try
23 End Sub
24 Private Sub MyListen()Sub MyListen()
25 Try
26 Dim ipAddress As System.Net.IPAddress = System.Net.Dns.Resolve(System.Net.Dns.GetHostName).AddressList(0)
27 tcpl = New System.Net.Sockets.TcpListener(ipAddress, 5656)
28 tcpl.Start()
29 While True
30 Dim s As System.Net.Sockets.Socket = tcpl.AcceptSocket()
31 Dim MyBuffer(1024) As Byte
32 Dim i As Integer
33 i = s.Receive(MyBuffer)
34 If i 0 Then
35 Dim lstrRec As String
36 Dim j As Integer
37 For j = 0 To i - 1
38 TextBox1.Text += Chr(MyBuffer(j)) ","
39 Next
40 End If
41 End While
42 Catch ex As Exception
43 MsgBox(ex.Message.ToString)
44 End Try
45 End Sub
46
47 Private Sub Button1_Click()Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
48 SendMessage("192.168.0.61", TextBox2.Text)
49 End Sub
关于串口通讯的问题：
很明显，你还不知道（不会、不习惯）使用事件驱动的方式接收数据。
建议你仔细看看串口组件（无论VB6还是VB.net）的OnComm事件，你的问题很容易解决。
关于以太网通讯：
在TCP通讯中端口确实可以重用，你百度一下“TCP端口重用”能查到很多示例。
但绝大多数情况下不推荐端口重用，而应该采取服务器端建立连接池的方法。
或者，干脆不用TCP，用UDP解决也可以。
既然从网上找的实例没问题，也许就是调用的时候没出来或者在检测网卡当中出现了问题。
都可以,可以用winsock,也可以自己重写SOCKET套接字.建议你如果工期紧,可以先用WINSOCK.当然最好是自己学用SOCKET套接字.这对未来开发网络通讯是很有帮助的.因为用WINSOCK有个毛病就是杀毒软件总会阻止
Private Sub Form_Load()
With Winsock1
.RemoteHost = "124.135.13.106" '对方的IP
.RemotePort = 1002 ' 对方的端口号
.Bind 1001 ' 本机的端口号
End With
End Sub
Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)
Dim strData As String
Winsock1.GetData strData '接收字节
List1.AddItem strData
End Sub
这个用UDP进行连接的。只不过是对单个机器进行的。
Microsoft.VisualBasic.Devices.Network.IsAvailable As Boolean
生成实例后可以通过此属性来获取是否联网的值，True代表已联网，False代表没有联网
Microsoft.VisualBasic.Devices.Network.NetworkAvailabilityChanged(ByVal Object, ByVal Microsoft.VisualBasic.Devices.NetworkAvailableEventArgs)
该事件是在电脑断开/连上互联网是引发的
其中：
e.IsNetworkAvailable
的功能同Microsoft.VisualBasic.Devices.Network.IsAvailable
实例:
Dim netListener As New Microsoft.VisualBasic.Devices.Network '生成实例
If netListener.IsAvailable = True Then
MsgBox("已联网")
Else
MsgBox("未联网")
End If
NetworkAvailabilityChanged实例：
WithEvents netListener As New Microsoft.VisualBasic.Devices.Network '生成实例
Private Sub OnNetworkChanged(ByVal Object, ByVal Microsoft.VisualBasic.Devices.NetworkAvailableEventArgs)Handles netListener.NetworkAvailabilityChanged
If e.IsNetworkAvailable = True Then
MsgBox("已联网")
Else
MsgBox("未联网")
End If
End Sub