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这是用VB.net实现的一个简单的P2P示例。利用了UDP打洞技术，分服务器端跟客户端，服务器端负责登陆记录用户的IP和端口及转发打洞消息。原理到处都有，这里就没有贴出来。这里贴出了VB.net的代码，供初学者交流，也欢迎高手点评…… 服务器端在启动成功后，输入help可以查看到服务器相关命令。 客户端在登陆成功后，输入help可以查看客户端相关命令(登陆时用户名随便)。 以下是服务器端: Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.Threading
Imports System.Collections
Module myUDPServer
#Region "全局变量"
Dim ServerSocket As New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)
Dim ipep As IPEndPoint = New IPEndPoint(IPAddress.Any, 11000)
Dim htUserList As New Hashtable '用来保存在线用户和用户的"IP和端口"
Dim userName(0) As String
Dim userIPEP(0) As IPEndPoint
Dim userTime(0) As Integer
Dim timerDelegate As New TimerCallback(AddressOf onLineTimeOut)
#End Region
#Region "参数"
'以下是客户端到服务器端的消息开头
Const LOGININ As String = "10" '请求登陆的消息|||消息形式:10+自己的用户名
Const LOGINOUT As String = "11" '请求登出的消息|||消息形式:11+自己的用户名
Const GETULIST As String = "12" '请求获得在线用户列表|||消息形式:12
Const P2PCONN As String = "13" '请求P2P连接的消息|||消息形式:13+自己的用户名+|+对方的用户名
Const HOLDLINE As String = "14" '保持连接.|||消息开式:14+自己的用户名
'以下是服务器到客户端的消息开头
Const HVUSER As String = "20" '用户名已存在
Const GETUSER As String = "21" '在线用户列表|||消息格式:21+用户名+EP
Const MAKHOLD As String = "22" '打洞命令|||消息格式:22+IP
Const LOGINOK As String = "23" '登陆成功
Const SERVCLS As String = "24" '服务器关闭
Const MSGEND As String = "25" '消息结束
'以下是服务器端的命名
Const EXITPRO As String = "EXIT" '退出命令
Const SHOWULIST As String = "SHOWUSER" '显示在线用户
Const HELP As String = "HELP" '显示帮助
#End Region
#Region "方法"
'主函数,程序入口
Sub Main()
'获得服务器的IP地址
Dim addressList As System.Net.IPAddress() = Dns.GetHostByName(Dns.GetHostName()).AddressList
Dim ServerIP As IPAddress = addressList(0)
ServerSocket.Bind(ipep)
Console.WriteLine("服务器正在启动....")
Console.WriteLine("服务器IP:" & ServerIP.ToString & " 正在监听" & ipep.Port.ToString & "端口")
Dim listenTH As New Thread(AddressOf listen)
listenTH.Start() '启用监听的线程
Console.WriteLine("服务器启动成功.....")
Dim timer As New Timer(timerDelegate, Nothing, 0, 5000)
Dim SVInput As String
While True
Console.Write("Server>")
SVInput = Console.ReadLine().ToUpper
Select Case SVInput
Case EXITPRO
listenTH.Abort()
ServerSocket.Close()
Exit Sub
Case SHOWULIST
showUser()
Case HELP
Console.Write("*********************************" & Chr(10) & Chr(13) & "exit:输出当前程序" & Chr(10) & Chr(13) & "showuser:显示当前在线用户例表" & Chr(10) & Chr(13) & "help:显示帮助" & Chr(10) & Chr(13) & "*********************************" & Chr(10) & Chr(13))
Case Else
Console.WriteLine("*********************************" & Chr(10) & Chr(13) & "笨瓜,你输入的不是有效的命令." & Chr(10) & Chr(13) & "*********************************")
End Select
End While
End Sub
'打印在线用户
Sub showUser()
Dim hava As Boolean = False
If userName.Length <> 0 Then
Dim i As Integer
For i = 1 To userName.Length - 1
If userName(i) <> "" Then
hava = True
Exit For
End If
Next
If hava = False Then
Console.WriteLine("*********************************" & Chr(10) & Chr(13) & "当前没有用户在线" & Chr(10) & Chr(13) & "*********************************")
Exit Sub
End If
Console.WriteLine("*********************************")
For i = 1 To userName.Length - 1
If userName(i) <> "" Then
Console.WriteLine("用户名:" & userName(i) & " 地址:" & userIPEP(i).ToString)
End If
Next
Console.WriteLine("*********************************")
Else
Console.WriteLine("*********************************" & Chr(10) & Chr(13) & "当前没有用户在线" & Chr(10) & Chr(13) & "*********************************")
End If
End Sub
'服务器监听函数
Sub listen()
While True
Try
Dim recv As Integer = 0
Dim data As [Byte]() = New Byte(1024) {}
Dim sender As New IPEndPoint(IPAddress.Any, 0)
Dim tempRemoteEP As EndPoint = CType(sender, EndPoint)
recv = ServerSocket.ReceiveFrom(data, tempRemoteEP)
'Console.WriteLine(Encoding.Unicode.GetString(data))
Dim msgHead As String = Encoding.Unicode.GetString(data, 0, 4)
Select Case msgHead
Case LOGININ
Dim LoginThing As String = userLogin(data, tempRemoteEP, recv)
If LoginThing = HVUSER Then
sendMsg(HVUSER, tempRemoteEP)
ElseIf LoginThing = LOGINOK Then
sendMsg(LOGINOK, tempRemoteEP)
End If
Case LOGINOUT
userloginout(data, recv)
Case GETULIST
Dim userinfo As String = getUserList()
sendMsg(userinfo, tempRemoteEP)
Case P2PCONN
questP2PConn(data, recv)
Case HOLDLINE
holdOnLine(data, recv)
End Select
Catch e As Exception
'Console.WriteLine(e.ToString)
End Try
End While
End Sub
'转发P2P连接请求
Private Sub questP2PConn(ByVal data() As Byte, ByVal recv As Integer)
Dim recvStr As String = Encoding.Unicode.GetString(data, 4, recv - 4)
Dim split() As String = recvStr.Split("|")
Dim fromEP As IPEndPoint
Dim toEP As IPEndPoint
Dim i As Integer
For i = 1 To userName.Length - 1
If userName(i) = split(0) Then
fromEP = userIPEP(i)
End If
If userName(i) = split(1) Then
toEP = userIPEP(i)
End If
Next
Dim holdbytes() As Byte = Encoding.Unicode.GetBytes(MAKHOLD & fromEP.ToString)
ServerSocket.SendTo(holdbytes, toEP)
End Sub
'函数.返回所有在线用户.其格式:用户名+|+用户IPEP+|
Private Function getUserList() As String
Dim userInfo As String = GETUSER
Dim i As Integer
For i = 1 To userName.Length - 1
If userName(i) <> "" Then
userInfo += userName(i) & "|" & userIPEP(i).ToString & "|"
End If
Next
Return userInfo
End Function
'用户登陆,直接返回登陆是否成功的值
Private Function userLogin(ByVal data As Byte(), ByVal userEP As IPEndPoint, ByVal recvCount As Integer) As String
Dim Uname As String = Encoding.Unicode.GetString(data, 4, recvCount - 4)
Dim Uinfobytes() As Byte
Dim i As Integer
Dim j As Integer
For i = 1 To userName.Length - 1
If Uname = userName(i) Then
Return HVUSER
End If
Next
For i = 1 To userName.Length - 1
If userName(i) = "" Then
userName(i) = Uname
userIPEP(i) = userEP
userTime(i) = 60
Console.Write(Chr(10) & Chr(13) & "*********************************" & Chr(10) & Chr(13) & Uname.Trim & "上线了." & "用户地址:" & userEP.ToString & Chr(10) & Chr(13) & "*********************************" & Chr(10) & Chr(13))
Console.Write("Server>")
Uinfobytes = Encoding.Unicode.GetBytes(LOGININ & userName(i) & "|" & userIPEP(i).ToString)
For j = 1 To userName.Length - 1
If userName(j) <> "" And userName(j) <> Uname Then
ServerSocket.SendTo(Uinfobytes, userIPEP(j))
End If
Next
Return LOGINOK
End If
Next
Dim userCount As Integer = userName.Length
ReDim Preserve userName(userCount)
ReDim Preserve userIPEP(userCount)
ReDim Preserve userTime(userCount)
userName(userName.Length - 1) = Uname
userIPEP(userIPEP.Length - 1) = userEP
userTime(userTime.Length - 1) = 60
Console.Write(Chr(10) & Chr(13) & "*********************************" & Chr(10) & Chr(13) & Uname.Trim & "上线了." & "用户地址:" & userEP.ToString & Chr(10) & Chr(13) & "*********************************" & Chr(10) & Chr(13))
Console.Write("Server>")
Uinfobytes = Encoding.Unicode.GetBytes(LOGININ & userName(userName.Length - 1) & "|" & userIPEP(userName.Length - 1).ToString)
For j = 1 To userName.Length - 1
If userName(j) <> "" And userName(j) <> Uname Then
ServerSocket.SendTo(Uinfobytes, userIPEP(j))
End If
Next
Return LOGINOK
End Function
'用户登出
Private Sub userloginout(ByVal data As Byte(), ByVal recvCount As Integer)
Dim i As Integer
Dim Uname As String = Encoding.Unicode.GetString(data, 4, recvCount - 4)
For i = 1 To userName.Length - 1
If Uname = userName(i) Then
Dim loginOutMsg As String = LOGINOUT & userName(i)
userName(i) = ""
userIPEP(i) = Nothing
userTime(i) = 0
Dim j As Integer
For j = 1 To userName.Length - 1
If userName(j) <> "" Then
sendMsg(loginOutMsg, userIPEP(j))
End If
Next
Console.WriteLine(Chr(10) & Chr(13) & "*********************************")
Console.WriteLine("用户" & Uname & "下线了.")
Console.WriteLine("*********************************")
Console.Write("Server>")
Exit For
End If
Next
End Sub
'保持用户在线的过程
Private Sub holdOnLine(ByVal data As Byte(), ByVal recvCount As Integer)
Dim Uname As String = Encoding.Unicode.GetString(data, 4, recvCount - 4)
Dim i As Integer
For i = 1 To userName.Length - 1
If Uname = userName(i) Then
userTime(i) = 60
Exit For
End If
Next
End Sub
'用户超时退出
Private Sub onLineTimeOut(ByVal state As [Object])
Dim i As Integer
For i = 1 To userName.Length - 1
If userTime(i) > 0 Then
userTime(i) -= 5
If userTime(i) <= 0 Then
Dim loginoutmsg As String = LOGINOUT & userName(i)
Console.WriteLine(Chr(10) & Chr(13) & "*********************************")
Console.WriteLine("用户" & userName(i) & "下线了.")
Console.WriteLine("*********************************")
Console.Write("Server>")
userName(i) = ""
userIPEP(i) = Nothing
Dim ULoginOutbytes() As Byte = Encoding.Unicode.GetBytes(loginoutmsg)
Dim j As Integer
For j = 1 To userName.Length - 1
If userName(j) <> "" Then
If userIPEP(j) Is Nothing Then
Else
ServerSocket.SendTo(ULoginOutbytes, userIPEP(j))
End If
End If
Next
End If
End If
Next
End Sub
'发送消息的函数
Sub sendMsg(ByVal msg As String, ByVal remoteEP As IPEndPoint)
Dim sendBytes As [Byte]() = Encoding.Unicode.GetBytes(msg)
Try
ServerSocket.SendTo(sendBytes, remoteEP)
Catch e As Exception
Console.WriteLine(e.ToString())
End Try
End Sub
#End Region
End Module
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