Imports System.NetImports System.ThreadingImports System.TextImports System.Net.Sockets Module Module1 Dim PortNumber As Integer = 1984 '侦听端口号 Dim Cmd As String = "Chat:" '提示符 Dim listener As Socket '侦听socket Dim tListener As Thread '侦听线程 Dim Prompted As Boolean = False '用于线程间同步的标志变量 Sub Main() Welcome() '欢迎信息 StartListener() '开始侦听 StartChatting() '准备好让用户发送消息 End Sub Private Sub Welcome() Dim txtMessage As String = vbCrLf & "Welcome! I am a console application for LAN chatting." & vbCrLf Console.WriteLine(txtMessage) End Sub Private Sub StartListener() Dim ready As Boolean = False Dim LocalPoint As IPEndPoint Dim msg As String While Not ready '向用户询问侦听端口号。用户可以直接回车，表示选择默认的。 msg = GetParams("===Now, enter the local port you want to listen(" & PortNumber & "):") If msg = "" Then msg = PortNumber Try PortNumber = Int(msg) LocalPoint = New IPEndPoint(Dns.GetHostByName(Dns.GetHostName).AddressList(0), PortNumber) listener = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp) listener.Bind(LocalPoint) ready = True Catch ex As Exception Console.WriteLine("※※※ERROR※※※ " & vbCrLf & ex.Message & vbCrLf) End Try End While tListener = New Thread(AddressOf thrListener) tListener.Start() End Sub Private Sub StartChatting() Dim RemoteHost As String = Dns.GetHostName Dim RemotePort As Integer = 1984 Dim RemotePoint As IPEndPoint Dim ready As Boolean = False Dim msg As String While Not ready '向用户询问发送消息的目标主机和端口。用户可以直接回车，表示选择默认的。 msg = GetParams("---enter the name of the one you want to chat with(" & RemoteHost & "):") If Not msg = "" Then RemoteHost = msg msg = GetParams("---enter the port number that guy listening at(" & RemotePort & "):") If msg = "" Then msg = RemotePort Try RemotePort = Int(msg) RemotePoint = New IPEndPoint(Dns.GetHostByName(RemoteHost).AddressList(0), RemotePort) ready = True Catch ex As Exception Console.WriteLine("※※※ERROR※※※ " & vbCrLf & ex.Message & vbCrLf) End Try End While Console.WriteLine() Console.WriteLine("OK, now you can chat. Type ""help"" to find out what you can do.") Console.WriteLine() Dim sender As New UdpClient Dim Message As String = Prompt() While True '用户现在可以开始发送消息 Prompted = False Select Case Message.ToLower Case "exit" Exit While Case "help" ShowHelp() Case Else Dim ByArr As Byte() = Encoding.Unicode.GetBytes(Message) sender.Send(ByArr, ByArr.Length, RemotePoint) '发出消息 End Select Message = Prompt() End While tListener.Abort() End End Sub Private Function GetParams(ByVal Msg As String) As String Console.Write(Msg) Return Console.ReadLine End Function Private Function Prompt() As String If Not Prompted Then Console.Write(Cmd) Prompted = True End If Return Console.ReadLine End Function Private Sub thrListener() '侦听线程 Dim bytes(4096) As Byte Dim NumGet As Integer Dim Msg As String While True Debug.WriteLine("Waiting for a message...") NumGet = listener.Receive(bytes) '接收 Prompted = False Msg = Encoding.Unicode.GetString(bytes, 0, NumGet) '与发送消息一样使用unicode编码 Console.WriteLine(vbCrLf & ">>>>>>>>>" & Msg & vbCrLf) If Not Prompted Then Console.Write(Cmd) Prompted = True End If End While End Sub Private Sub ShowHelp() Console.WriteLine("") Console.WriteLine("========================================================================") Console.WriteLine("This program is very simple, you can type ""exit"" to exit program.") Console.WriteLine("========================================================================") Console.WriteLine("") End Sub End Module

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