UDP打洞原理及代码
2024-08-27 15:09:49
来源：http://www.fenbi360.net/Content.aspx?id=1021&t=jc
UDP"打洞"原理
1. NAT分类
根据Stun协议(RFC3489),NAT大致分为下面四类
1) Full Cone
这种NAT内部的机器A连接过外网机器C后,NAT会打开一个端口.然后外网的任何发到这个打开的端口的UDP数据报都可以到达A.不管是不是C发过来的.
例如 A:192.168.8.100 NAT:202.100.100.100 C:292.88.88.88
A(192.168.8.100:5000) -> NAT(202.100.100.100 : 8000) -> C(292.88.88.88:2000)
任何发送到 NAT(202.100.100.100:8000)的数据都可以到达A(192.168.8.100:5000)
2) Restricted Cone
这种NAT内部的机器A连接过外网的机器C后,NAT打开一个端口.然后C可以用任何端口和A通信.其他的外网机器不行.
例如 A:192.168.8.100 NAT:202.100.100.100 C:292.88.88.88
A(192.168.8.100:5000) -> NAT(202.100.100.100 : 8000) -> C(292.88.88.88:2000)
任何从C发送到 NAT(202.100.100.100:8000)的数据都可以到达A(192.168.8.100:5000)
3) Port Restricted Cone
这种NAT内部的机器A连接过外网的机器C后,NAT打开一个端口.然后C可以用原来的端口和A通信.其他的外网机器不行.
例如 A:192.168.8.100 NAT:202.100.100.100 C:292.88.88.88
A(192.168.8.100:5000) -> NAT(202.100.100.100 : 8000) -> C(292.88.88.88:2000)
C(202.88.88.88:2000)发送到 NAT(202.100.100.100:8000)的数据都可以到达A(192.168.8.100:5000)
以上三种NAT通称Cone NAT.我们只能用这种NAT进行UDP打洞.
4) Symmetic
对于这种NAT.连接不同的外部目标.原来NAT打开的端口会变化.而Cone NAT不会.虽然可以用端口猜测.但是成功的概率很小.因此放弃这种NAT的UDP打洞.
2. UDP hole punching
对于Cone NAT.要采用UDP打洞.需要一个公网机器C来充当”介绍人”.内网的A,B先分别和C通信.打开各自的NAT端口.C这个时候知道A,B的公网IP: Port. 现在A和B想直接连接.比如A给B发.除非B是Full Cone.否则不能通信.反之亦然.但是我们可以这样.
A要连接B.A给B发一个UDP包.同时.A让那个介绍人给B发一个命令,让B同时给A发一个UDP包.这样双方的NAT都会记录对方的IP,然后就会允许互相通信.
3. 同一个NAT后面的情况
如果A,B在同一个NAT后面.如果用上面的技术来进行互连.那么如果NAT支持loopback(就是本地到本地的转换),A,B可以连接,但是比较浪费带宽和NAT.有一种办法是,A,B和介绍人通信的时候,同时把自己的local IP也告诉服务器.A,B通信的时候,同时发local ip和公网IP.谁先到就用哪个IP.但是local ip就有可能不知道发到什么地方去了.比如A,B在不同的NAT后面但是他们各自的local ip段一样.A给B的local IP发的UDP就可能发给自己内部网里面的某某某了.
还有一个办法是服务器来判断A,B是否在一个NAT后面.(网络拓朴不同会不会有问题?)
WellKnown.cs
//WellKnown公用库
using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Net;
using System.Net.Sockets;
using System.Collections; namespace P2PWellKnown
{
/// <summary>
/// UDP用户登录事件委托
/// </summary>
/// <param name="sender">事件源对象</param>
/// <param name="e">事件实体</param>
public delegate void UdpUserLogInDelegate(object sender, UDPSockEventArgs e); /// <summary>
/// 一般UDP消息事件委托
/// </summary>
/// <param name="sender">事件源对象</param>
/// <param name="e">事件实体</param>
public delegate void UdpMessageDelegate(object sender, UDPSockEventArgs e); /// <summary>
/// 初始化一个新连接的事件委托
/// </summary>
/// <param name="sender">事件源对象</param>
/// <param name="e">事件实体</param>
public delegate void UdpNewConnectDelegate(object sender, UDPSockEventArgs e); /// <summary>
/// P2P共享数据类
/// </summary>
public class P2PConsts
{
/// <summary>
/// UDP服务器监听端口
/// </summary>
public const int UDP_SRV_PORT = ; /// <summary>
///TCP服务器监听端口
/// </summary>
public const int TCP_SRV_PORT = ;
} /// <summary>
/// FormatterHelper 序列化，反序列化消息的帮助类
/// </summary>
public class FormatterHelper
{ public static byte[] Serialize(object obj)
{
BinaryFormatter binaryF = new BinaryFormatter();
MemoryStream ms = new MemoryStream( * );
binaryF.Serialize(ms, obj);
ms.Seek(, SeekOrigin.Begin);
byte[] buffer = new byte[(int)ms.Length];
ms.Read(buffer, , buffer.Length);
ms.Close();
return buffer;
} public static object Deserialize(byte[] buffer)
{
BinaryFormatter binaryF = new BinaryFormatter();
MemoryStream ms = new MemoryStream(buffer, , buffer.Length, false);
object obj = binaryF.Deserialize(ms);
ms.Close();
return obj;
} } /// <summary>
/// 用于承载UDPSock信息的事件类
/// </summary>
public class UDPSockEventArgs : EventArgs
{
/// <summary>
/// 要承载的消息
/// </summary>
private string m_strMsg; /// <summary>
/// 用户信息
/// </summary>
private string m_strUserName; /// <summary>
/// 触发该事件的公共终端
/// </summary>
private IPEndPoint m_EndPoint; /// <summary>
/// 初始化UDPSock事件
/// </summary>
/// <param name="sMsg">用户发送的信息</param>
public UDPSockEventArgs(string sMsg)
: base()
{
this.m_strMsg = sMsg;
} /// <summary>
/// 远端用户名
/// </summary>
public string RemoteUserName
{
get
{
return m_strUserName;
}
set
{
m_strUserName = value;
}
} /// <summary>
/// 一般套接字消息
/// </summary>
public string SockMessage
{
get
{
return m_strMsg;
}
set
{
m_strMsg = value;
}
} /// <summary>
/// 公共远端节点
/// </summary>
public IPEndPoint RemoteEndPoint
{
get
{
return m_EndPoint;
}
set
{
m_EndPoint = value;
}
}
}
}
UDPP2PSock.cs
//UDPP2PSock.cs
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading; using P2PWellKnown; namespace UDPP
{
/// <summary>
/// UDPP2P套接字管理类
/// </summary>
public class UDPP2PSock
{
/// <summary>
/// 用户登录事件
/// </summary>
public event UdpUserLogInDelegate OnUserLogInU; /// <summary>
/// 一般UDP消息事件
/// </summary>
public event UdpMessageDelegate OnSockMessageU; /// <summary>
/// 初始化一个新连接事件
/// </summary>
public event UdpNewConnectDelegate OnNewConnectU; /// <summary>
/// UDP服务器
/// </summary>
private UdpClient m_udpServer; /// <summary>
/// UDP客户端
/// </summary>
private UdpClient m_udpClient; /// <summary>
/// 服务器实际上在本地机器上监听的
/// 端口，用于当一台计算机上同时启
/// 动两个可两以上服务器进程时，标
/// 识不同的服务器进程
/// </summary>
private int m_iMyServerPort; /// <summary>
/// 客户端在本地机器上实际使用的端口，
/// 用于当一台计算机上同时有两个或两
/// 个以上客户端进程在运行时，标识不
/// 同的客户端进程
/// </summary>
private int m_iMyClientPort; /// <summary>
/// 标识是否已成功创服务器
/// </summary>
private bool m_bServerCreated; /// <summary>
/// 标识是否已成功创建客户端
/// </summary>
private bool m_bClientCreated; /// <summary>
/// 服务器使用的线程
/// </summary>
private Thread m_serverThread; /// <summary>
/// 客户端使用的线程
/// </summary>
private Thread m_clientThread; /// <summary>
/// 打洞线程
/// </summary>
//private Thread m_burrowThread; /// <summary>
/// 远端节点
/// </summary>
private IPEndPoint m_remotePoint; /// <summary>
/// 当前进程作为客户端的公共终端
/// </summary>
private string m_strMyPublicEndPoint; /// <summary>
/// 当前进程作为客户端的私有终端
/// </summary>
private string m_strMyPrivateEndPoint; /// <summary>
/// 用于接受信息的 StringBuilder实例
/// </summary>
private StringBuilder m_sbResponse = new StringBuilder(); /// <summary>
/// P2P打洞时标识是否收到回应消息
/// </summary>
private bool m_bRecvAck = false; /// <summary>
/// 请求向其方向打洞的私有终端
/// </summary>
private IPEndPoint m_requestPrivateEndPoint; /// <summary>
/// 请求向其方向打洞的公共终端
/// </summary>
private IPEndPoint m_requestPublicEndPoint; /// <summary>
/// 打洞消息要发向的节点
/// </summary>
private ToEndPoint m_toEndPoint; /// <summary>
/// 用于标识是否已经和请求客户端建立点对连接
/// </summary>
//private bool m_bHasConnected=false ; /// <summary>
/// 创建服务器或客户端的最大尝试
/// 次数，为（65536-60000），防止
/// 因不能创建而限入死循环或使用
/// 无效端口
/// </summary>
private const int MAX_CREATE_TRY = ; /// <summary>
/// 打洞时尝试连接的最大尝试次数
/// </summary>
private const int MAX_CONNECT_TRY = ; /// <summary>
/// 构造函数，初始化UDPP2P实例
/// </summary>
public UDPP2PSock()
{
m_iMyServerPort = P2PConsts.UDP_SRV_PORT;
m_iMyClientPort = ;
m_bClientCreated = false;
m_bServerCreated = false;
m_toEndPoint = new ToEndPoint();
m_serverThread = new Thread(new ThreadStart(RunUDPServer));
m_clientThread = new Thread(new ThreadStart(RunUDPClient));
//m_burrowThread = new Thread(new ThreadStart(BurrowProc));
} /// <summary>
/// 创建UDP 服务器
/// </summary>
public void CreateUDPSever()
{
int iTryNum = ; //开始尝试创建服务器
while (!m_bServerCreated && iTryNum < MAX_CREATE_TRY)
{
try
{
m_udpServer = new UdpClient(m_iMyServerPort);
m_bServerCreated = true;
}
catch
{
m_iMyServerPort++;
iTryNum++;
}
} //创建失败，抛出异常
if (!m_bServerCreated && iTryNum == MAX_CREATE_TRY)
{
throw new Exception("创建服务器尝试失败！");
}
m_serverThread.Start(); } /// <summary>
/// 创建UDP客户端
/// </summary>
/// <param name="strServerIP"& gt;服务器IP</param>
/// <param name="iServerPort"& gt;服务器端口</param>
public void CreateUDPClient(string strServerIP, int iServerPort)
{
int iTryNum = ; //开始尝试创建服务器
while (!m_bClientCreated && iTryNum < MAX_CREATE_TRY)
{
try
{
m_udpClient = new UdpClient(m_iMyClientPort);
m_bClientCreated = true;
string strIPAddress = (System.Net.Dns.GetHostAddresses("localhost")[]).ToString();
m_strMyPrivateEndPoint = strIPAddress + ":" + m_iMyClientPort.ToString();
}
catch
{
m_iMyClientPort++;
iTryNum++;
}
} //创建失败，抛出异常
if (!m_bClientCreated && iTryNum == MAX_CREATE_TRY)
{
throw new Exception("创建客户端尝试失败！");
} IPEndPoint hostPoint = new IPEndPoint(IPAddress.Parse(strServerIP), iServerPort);
string strLocalIP = (System.Net.Dns.GetHostAddresses("localhost"))[].ToString();
SendLocalPoint(strLocalIP, m_iMyClientPort, hostPoint);
m_clientThread.Start();
} /// <summary>
/// 运行UDP 服务器
/// </summary>
private void RunUDPServer()
{
while (true)
{
byte[] msgBuffer = m_udpServer.Receive(ref m_remotePoint);
m_sbResponse.Append(System.Text.Encoding.Default.GetString(msgBuffer));
CheckCommand();
Thread.Sleep();
}
} /// <summary>
/// 运行UDP客户端
/// </summary>
private void RunUDPClient()
{
while (true)
{
byte[] msgBuffer = m_udpClient.Receive(ref m_remotePoint);
m_sbResponse.Append(System.Text.Encoding.Default.GetString(msgBuffer));
CheckCommand();
Thread.Sleep();
}
} /// <summary>
/// 销毁UDP 服务器
/// </summary>
public void DisposeUDPServer()
{
m_serverThread.Abort();
m_udpServer.Close();
} /// <summary>
/// 销毁UDP客房端
/// </summary>
public void DisposeUDPClient()
{
m_clientThread.Abort();
m_udpClient.Close();
} /// <summary>
/// 发送消息
/// </summary>
/// <param name="strMsg"& gt;消息内容</param>
/// <param name="REP"& gt;接收节点</param>
public void SendData(string strMsg, IPEndPoint REP)
{
byte[] byMsg = System.Text.Encoding.Default.GetBytes(strMsg.ToCharArray());
m_udpClient.Send(byMsg, byMsg.Length, REP);
} /// <summary>
/// 发送消息，服务器专用
/// </summary>
/// <param name="strMsg"& gt;消息内容</param>
/// <param name="REP"& gt;接收节点</param>
private void ServerSendData(string strMsg, IPEndPoint REP)
{
byte[] byMsg = System.Text.Encoding.Default.GetBytes(strMsg.ToCharArray());
m_udpServer.Send(byMsg, byMsg.Length, REP);
} /// <summary>
/// 发送本地节点信息
/// </summary>
/// <param name="strLocalIP"& gt;本地IP</param>
/// <param name="iLocalPort"& gt;本地端口</param>
public void SendLocalPoint(string strLocalIP, int iLocalPort, IPEndPoint REP)
{
string strLocalPoint = "\x01\x02" + strLocalIP + ":" + iLocalPort.ToString() + "\x02\x01";
SendData(strLocalPoint, REP);
} /// <summary>
/// 同时向指定的终端（包括公共终端和私有终端）打洞
/// </summary>
/// <param name="pubEndPoint"& gt;公共终端</param>
/// <param name="prEndPoint"& gt;私有终端</param>
/// <returns>打洞成功返回true,否则返回false</returns>
public void StartBurrowTo(IPEndPoint pubEndPoint, IPEndPoint prEndPoint)
{
Thread burrowThread = new Thread(new ThreadStart(BurrowProc));
m_toEndPoint.m_privateEndPoint = prEndPoint;
m_toEndPoint.m_publicEndPoint = pubEndPoint;
burrowThread.Start();
} /// <summary>
/// 打洞线程
/// </summary>
private void BurrowProc()
{
IPEndPoint prEndPoint = m_toEndPoint.m_privateEndPoint;
IPEndPoint pubEndPoint = m_toEndPoint.m_publicEndPoint;
int j = ;
for (int i = ; i < MAX_CONNECT_TRY; i++)
{
SendData("\x01\x07\x07\x01", prEndPoint);
SendData("\x01\x07\x07\x01", pubEndPoint); // 等待接收线程标记修改
for (j = ; j < MAX_CONNECT_TRY; j++)
{
if (m_bRecvAck)
{
m_bRecvAck = false;
SendData("\x01\x07\x07\x01", prEndPoint);
Thread.Sleep();
SendData("\x01\x07\x07\x01", pubEndPoint); UDPSockEventArgs args = new UDPSockEventArgs("");
args.RemoteEndPoint = pubEndPoint;
if (OnNewConnectU != null)
{
OnNewConnectU(this, args);
}
//Thread .Sleep (System .Threading.Timeout .Infinite );
return;
}
else
{
Thread.Sleep();
}
} //如果没有收到目标主机的回应，表明本次打
// 洞尝试失败,等待100毫秒后尝试下一次打洞
Thread.Sleep();
} //MAX_CONNECT_TRY 尝试都失败，表明打洞失败，抛出异常
//throw new Exception(" 打洞失败！");
System.Windows.Forms.MessageBox.Show("打洞失败！");////////////
} /// <summary>
/// 转发打洞请求消息，在服务器端使用
/// </summary>
/// <param name="strSrcPrEndpoint"& gt;请求转发的源私有终端</param>
/// <param name="strSrcPubEndPoint"& gt;请求转发的源公共终端</param>
/// <param name="REP"& gt;转发消息到达的目的终端</param>
public void SendBurrowRequest(string strSrcPrEndpoint, string strSrcPubEndPoint, IPEndPoint REP)
{
string strBurrowMsg = "\x04\x07" + strSrcPrEndpoint + " " + strSrcPubEndPoint + "\x07\x04";
ServerSendData(strBurrowMsg, REP);
} /// <summary>
/// 检查字符串中的命令
/// </summary>
private void CheckCommand()
{
int nPos;
string strCmd = m_sbResponse.ToString(); //如果接收远端用户名
if ((nPos = strCmd.IndexOf("\x01\x02")) > -)
{
ReceiveName(strCmd, nPos); // 反馈公共终给端远端主机
string strPubEPMsg = "\x03\x07" + m_remotePoint.ToString() + "\x07\x03";
SendData(strPubEPMsg, m_remotePoint); return;
} //如果接收我的公共终端
if ((nPos = strCmd.IndexOf("\x03\x07")) > -)
{
ReceiveMyPublicEndPoint(strCmd, nPos);
return;
} //如果是打洞请求消息
if ((nPos = strCmd.IndexOf("\x04\x07")) > -)
{
ReceiveAndSendAck(strCmd, nPos);
return;
} //如果是打洞回应消息
if ((nPos = strCmd.IndexOf("\x01\x07")) > -)
{
m_bRecvAck = true;
int nPos2 = strCmd.IndexOf("\x07\x01");
if (nPos2 > -)
{
m_sbResponse.Remove(nPos, nPos2 - nPos + );
} return;
} //一般聊天消息
m_sbResponse.Remove(, strCmd.Length);
RaiseMessageEvent(strCmd);
} /// <summary>
/// 接收远端用户名
/// </summary>
/// <param name="strCmd"& gt;包含用户名的控制信息</param>
/// <param name="nPos"></param>
private void ReceiveName(string strCmd, int nPos)
{
int nPos2 = strCmd.IndexOf("\x02\x01");
if (nPos2 == -)
{
return;
}
m_sbResponse.Remove(nPos, nPos2 - nPos + ); string strUserName = strCmd.Substring(nPos + , nPos2 - nPos - );
UDPSockEventArgs e = new UDPSockEventArgs("");
e.RemoteUserName = strUserName;
e.RemoteEndPoint = m_remotePoint; //触发用户登录事件
if (OnUserLogInU != null)
{
OnUserLogInU(this, e);
}
} /// <summary>
/// 接收打洞请求的消息并发送回应
/// </summary>
/// <param name="strCmd"></param>
/// <param name="nPos"></param>
private void ReceiveAndSendAck(string strCmd, int nPos)
{
int nPos2 = strCmd.IndexOf("\x07\x04");
if (nPos2 == -)
{
return;
}
m_sbResponse.Remove(nPos, nPos2 - nPos + ); string strBurrowMsg = strCmd.Substring(nPos + , nPos2 - nPos - ); string[] strSrcPoint = strBurrowMsg.Split(' '); //分析控制字符串包含的节点信息
string[] strPrEndPoint = strSrcPoint[].Split(':');
string[] strPubEndPoint = strSrcPoint[].Split(':');
m_requestPrivateEndPoint = new IPEndPoint(IPAddress.Parse(strPrEndPoint[]), int.Parse(strPrEndPoint[]));
m_requestPublicEndPoint = new IPEndPoint(IPAddress.Parse(strPubEndPoint[]), int.Parse(strPubEndPoint[])); //向请求打洞终端的方向打洞
StartBurrowTo(m_requestPublicEndPoint, m_requestPrivateEndPoint);
} /// <summary>
/// 接收我的公共终端
/// </summary>
/// <param name="strCmd"& gt;包含公共终端的控制信息</param>
/// <param name="nPos"& gt;控制字符串的起始位置</param>
private void ReceiveMyPublicEndPoint(string strCmd, int nPos)
{
int nPos2 = strCmd.IndexOf("\x07\x03");
if (nPos2 == -)
{
return;
}
m_sbResponse.Remove(nPos, nPos2 - nPos + ); m_strMyPublicEndPoint = strCmd.Substring(nPos + , nPos2 - nPos - );
} /// <summary>
/// 触发一般UDP消息事件
/// </summary>
/// <param name="strMsg"& gt;消息内容</param>
private void RaiseMessageEvent(string strMsg)
{
UDPSockEventArgs args = new UDPSockEventArgs("");
args.SockMessage = strMsg;
args.RemoteEndPoint = m_remotePoint;
if (OnSockMessageU != null)
{
OnSockMessageU(this, args);
}
} /// <summary>
/// 获取当前进程作为客户端的公共终端
/// </summary>
public string MyPublicEndPoint
{
get
{
return m_strMyPublicEndPoint;
}
} /// <summary>
/// 获取当前进程作为客户端的私有终端
/// </summary>
public string MyPrivateEndPoint
{
get
{
return m_strMyPrivateEndPoint;
}
}
} /// <summary>
/// 保存打洞消息要发向的节点信息
/// </summary>
class ToEndPoint
{
/// <summary>
/// 私有节点
/// </summary>
public IPEndPoint m_privateEndPoint; /// <summary>
/// 公共节点
/// </summary>
public IPEndPoint m_publicEndPoint;
}
}
关于如何使用上述程序包的一些说明：
主要程序的初始化，参考代码如下：
using UDPP;
using P2PWellKnown; //创建UDP服务器和客户端
try
{
string strServerIP = "127.0.0.1";
UDPP2PSock udpSock = new UDPP2PSock();
udpSock.OnUserLogInU += new UdpUserLogInDelegate(OnUserLogInU);
udpSock.OnNewConnectU += new UdpNewConnectDelegate(OnNewConnectU);
udpSock.CreateUDPSever();
udpSock.CreateUDPClient(strServerIP, P2PConsts.UDP_SRV_PORT);
}
catch (Exception ex)
{ }
经上面的初始化后，就可以使用类UDPP2PSock中的方法了。
注：
udpSock.OnUserLogInU +=new UdpUserLogInDelegate(OnUserLogInU);
udpSock.OnNewConnectU +=new UdpNewConnectDelegate(OnNewConnectU);
中的OnUserLogInU和OnNewConnectU是事件名称,如
private void test(object sender, UDPSockEventArgs e)
{
MessageBox.Show("ok");
}
出处：http://www.cnblogs.com/hcbin/archive/2010/04/10/1709019.html
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