論壇上經常有對P2P原理的討論，但是討論歸討論，很少有實質的東西產生（源代碼）。呵呵，在這里我就用自己實現的一個源代碼來說明UDP穿越NAT的原理。 首先先介紹一些基本概念： NAT(Network Address Translators)，網絡地址轉換：網絡地址轉換是在IP地址日益缺乏的情況下產生的，它的主要目的就是為了能夠地址重用。NAT分為兩大類，基本的NAT和NAPT(Network Address/Port Translator)。 最開始NAT是運行在路由器上的一個功能模塊。 最先提出的是基本的NAT，它的產生基于如下事實：一個私有網絡（域）中的節點中只有很少的節點需要與外網連接（呵呵，這是在上世紀90年代中期提出的）。那么這個子網中其實只有少數的節點需要全球唯一的IP地址，其他的節點的IP地址應該是可以重用的。 因此，基本的NAT實現的功能很簡單，在子網內使用一個保留的IP子網段，這些IP對外是不可見的。子網內只有少數一些IP地址可以對應到真正全球唯一的IP地址。如果這些節點需要訪問外部網絡，那么基本NAT就負責將這個節點的子網內IP轉化為一個全球唯一的IP然后發送出去。(基本的NAT會改變IP包中的原IP地址，但是不會改變IP包中的端口) 關于基本的NAT可以參看RFC 1631 另外一種NAT叫做NAPT，從名稱上我們也可以看得出，NAPT不但會改變經過這個NAT設備的IP數據報的IP地址，還會改變IP數據報的TCP/UDP端口。基本NAT的設備可能我們見的不多（呵呵，我沒有見到過），NAPT才是我們真正討論的主角。看下圖： Server S1 18.181.0.31:1235 | ^ Session 1 (A-S1) ^ | | 18.181.0.31:1235 | | v 155.99.25.11:62000 v | | NAT 155.99.25.11 | ^ Session 1 (A-S1) ^ | | 18.181.0.31:1235 | | v 10.0.0.1:1234 v | | Client A 10.0.0.1:1234 有一個私有網絡10.*.*.*，Client A是其中的一臺計算機，這個網絡的網關（一個NAT設備）的外網IP是155.99.25.11(應該還有一個內網的IP地址，比如10.0.0.10)。如果Client A中的某個進程（這個進程創建了一個UDP Socket,這個Socket綁定1234端口）想訪問外網主機18.181.0.31的1235端口，那么當數據包通過NAT時會發生什么事情呢？ 首先NAT會改變這個數據包的原IP地址，改為155.99.25.11。接著NAT會為這個傳輸創建一個Session（Session是一個抽象的概念，如果是TCP，也許Session是由一個SYN包開始，以一個FIN包結束。而UDP呢，以這個IP的這個端口的第一個UDP開始，結束呢，呵呵，也許是幾分鐘，也許是幾小時，這要看具體的實現了）并且給這個Session分配一個端口，比如62000，然后改變這個數據包的源端口為62000。所以本來是（10.0.0.1:1234->18.181.0.31:1235）的數據包到了互聯網上變為了（155.99.25.11:62000->18.181.0.31:1235）。 一旦NAT創建了一個Session后，NAT會記住62000端口對應的是10.0.0.1的1234端口，以后從18.181.0.31發送到62000端口的數據會被NAT自動的轉發到10.0.0.1上。（注意：這里是說18.181.0.31發送到62000端口的數據會被轉發，其他的IP發送到這個端口的數據將被NAT拋棄）這樣Client A就與Server S1建立以了一個連接。 呵呵，上面的基礎知識可能很多人都知道了，那么下面是關鍵的部分了。 看看下面的情況： Server S1 Server S2 18.181.0.31:1235 138.76.29.7:1235 | | | | +----------------------+----------------------+ | ^ Session 1 (A-S1) ^ | ^ Session 2 (A-S2) ^ | 18.181.0.31:1235 | | | 138.76.29.7:1235 | v 155.99.25.11:62000 v | v 155.99.25.11:62000 v | Cone NAT 155.99.25.11 | ^ Session 1 (A-S1) ^ | ^ Session 2 (A-S2) ^ | 18.181.0.31:1235 | | | 138.76.29.7:1235 | v 10.0.0.1:1234 v | v 10.0.0.1:1234 v | Client A 10.0.0.1:1234 接上面的例子，如果Client A的原來那個Socket(綁定了1234端口的那個UDP Socket)又接著向另外一個Server S2發送了一個UDP包，那么這個UDP包在通過NAT時會怎么樣呢？ 這時可能會有兩種情況發生，一種是NAT再次創建一個Session，并且再次為這個Session分配一個端口號（比如：62001）。另外一種是NAT再次創建一個Session，但是不會新分配一個端口號，而是用原來分配的端口號62000。前一種NAT叫做Symmetric NAT，后一種叫做Cone NAT。我們期望我們的NAT是第二種，呵呵，如果你的NAT剛好是第一種，那么很可能會有很多P2P軟件失靈。（可以慶幸的是，現在絕大多數的NAT屬于后者，即Cone NAT） 好了，我們看到，通過NAT,子網內的計算機向外連結是很容易的（NAT相當于透明的，子網內的和外網的計算機不用知道NAT的情況）。 但是如果外部的計算機想訪問子網內的計算機就比較困難了（而這正是P2P所需要的）。 那么我們如果想從外部發送一個數據報給內網的計算機有什么辦法呢？首先，我們必須在內網的NAT上打上一個“洞”（也就是前面我們說的在NAT上建立一個Session），這個洞不能由外部來打，只能由內網內的主機來打。而且這個洞是有方向的，比如從內部某臺主機（比如：192.168.0.10）向外部的某個IP(比如：219.237.60.1)發送一個UDP包，那么就在這個內網的NAT設備上打了一個方向為219.237.60.1的“洞”，（這就是稱為UDP Hole Punching的技術）以后219.237.60.1就可以通過這個洞與內網的192.168.0.10聯系了。（但是其他的IP不能利用這個洞）。 ---------------------------------------------------------- 現在該輪到我們的正題P2P了。有了上面的理論，實現兩個內網的主機通訊就差最后一步了：那就是雞生蛋還是蛋生雞的問題了，兩邊都無法主動發出連接請求，誰也不知道誰的公網地址，那我們如何來打這個洞呢？我們需要一個中間人來聯系這兩個內網主機。 現在我們來看看一個P2P軟件的流程，以下圖為例： Server S （219.237.60.1） | | +----------------------+----------------------+ | | NAT A (外網IP:202.187.45.3) NAT B (外網IP:187.34.1.56) | (內網IP:192.168.0.1) | (內網IP:192.168.0.1) | | Client A (192.168.0.20:4000) Client B (192.168.0.10:40000) 首先，Client A登錄服務器，NAT A為這次的Session分配了一個端口60000，那么Server S收到的Client A的地址是202.187.45.3:60000，這就是Client A的外網地址了。同樣，Client B登錄Server S，NAT B給此次Session分配的端口是40000，那么Server S收到的B的地址是187.34.1.56:40000。 此時，Client A與Client B都可以與Server S通信了。如果Client A此時想直接發送信息給Client B，那么他可以從Server S那兒獲得B的公網地址187.34.1.56:40000，是不是Client A向這個地址發送信息Client B就能收到了呢？答案是不行，因為如果這樣發送信息，NAT B會將這個信息丟棄（因為這樣的信息是不請自來的，為了安全，大多數NAT都會執行丟棄動作）。現在我們需要的是在NAT B上打一個方向為202.187.45.3（即Client A的外網地址）的洞，那么Client A發送到187.34.1.56:40000的信息,Client B就能收到了。這個打洞命令由誰來發呢，呵呵，當然是Server S。 總結一下這個過程：如果Client A想向Client B發送信息，那么Client A發送命令給Server S，請求Server S命令Client B向Client A方向打洞。呵呵，是不是很繞口，不過沒關系，想一想就很清楚了，何況還有源代碼呢（侯老師說過：在源代碼面前沒有秘密 8）），然后Client A就可以通過Client B的外網地址與Client B通信了。 注意：以上過程只適合于Cone NAT的情況，如果是Symmetric NAT，那么當Client B向Client A打洞的端口已經重新分配了，Client B將無法知道這個端口（如果Symmetric NAT的端口是順序分配的，那么我們或許可以猜測這個端口號，可是由于可能導致失敗的因素太多，我們不推薦這種猜測端口的方法）。 下面是一個模擬P2P聊天的過程的源代碼，過程很簡單，P2PServer運行在一個擁有公網IP的計算機上，P2PClient運行在兩個不同的NAT后（注意，如果兩個客戶端運行在一個NAT后，本程序很可能不能運行正常，這取決于你的NAT是否支持loopback translation，詳見http://midcom-p2p.sourceforge.net/draft-ford-midcom-p2p-01.txt，當然，此問題可以通過雙方先嘗試連接對方的內網IP來解決，但是這個代碼只是為了驗證原理，并沒有處理這些問題），后登錄的計算機可以獲得先登錄計算機的用戶名，后登錄的計算機通過send username message的格式來發送消息。如果發送成功，說明你已取得了直接與對方連接的成功。 程序現在支持三個命令：send , getu , exit send格式：send username message 功能：發送信息給username getu格式：getu 功能：獲得當前服務器用戶列表 exit格式：exit 功能：注銷與服務器的連接（服務器不會自動監測客戶是否吊線） C語言代碼
P2PServer.c
/* P2P 程序服務端
*
* 文件名：P2PServer.c
*
* 日期：2004-5-21
*
* 作者：shootingstars(zhouhuis22@sina.com)
*
*/
#pragma comment(lib, "ws2_32.lib")
#include "windows.h"
#include "..\proto.h"
#include "..\Exception.h"
UserList ClientList;
void InitWinSock()
{
WSADATA wsaData;
if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
{
printf("Windows sockets 2.2 startup");
throw Exception("");
}
else{
printf("Using %s (Status: %s)\n",
wsaData.szDescription, wsaData.szSystemStatus);
printf("with API versions %d.%d to %d.%d\n\n",
LOBYTE(wsaData.wVersion), HIBYTE(wsaData.wVersion),
LOBYTE(wsaData.wHighVersion), HIBYTE(wsaData.wHighVersion));
}
}
SOCKET mksock(int type)
{
SOCKET sock = socket(AF_INET, type, 0);
if (sock < 0)
{
printf("create socket error");
throw Exception("");
}
return sock;
}
stUserListNode GetUser(char *username)
{
for(UserList::iterator UserIterator=ClientList.begin();
UserIterator!=ClientList.end();
++UserIterator)
{
if( strcmp( ((*UserIterator)->userName), username) == 0 )
return *(*UserIterator);
}
throw Exception("not find this user");
}
int main(int argc, char* argv[])
{
try{
InitWinSock();
SOCKET PrimaryUDP;
PrimaryUDP = mksock(SOCK_DGRAM);
sockaddr_in local;
local.sin_family=AF_INET;
local.sin_port= htons(SERVER_PORT);
local.sin_addr.s_addr = htonl(INADDR_ANY);
int nResult=bind(PrimaryUDP,(sockaddr*)&local,sizeof(sockaddr));
if(nResult==SOCKET_ERROR)
throw Exception("bind error");
sockaddr_in sender;
stMessage recvbuf;
memset(&recvbuf,0,sizeof(stMessage));
// 開始主循環.
// 主循環負責下面幾件事情:
// 一:讀取客戶端登陸和登出消息,記錄客戶列表
// 二:轉發客戶p2p請求
for(;;)
{
int dwSender = sizeof(sender);
int ret = recvfrom(PrimaryUDP, (char *)&recvbuf, sizeof(stMessage), 0, (sockaddr *)&sender, &dwSender);
if(ret <= 0)
{
printf("recv error");
continue;
}
else
{
int messageType = recvbuf.iMessageType;
switch(messageType){
case LOGIN:
{
// 將這個用戶的信息記錄到用戶列表中
printf("has a user login : %s\n", recvbuf.message.loginmember.userName);
stUserListNode *currentuser = new stUserListNode();
strcpy(currentuser->userName, recvbuf.message.loginmember.userName);
currentuser->ip = ntohl(sender.sin_addr.S_un.S_addr);
currentuser->port = ntohs(sender.sin_port);
ClientList.push_back(currentuser);
// 發送已經登陸的客戶信息
int nodecount = (int)ClientList.size();
sendto(PrimaryUDP, (const char*)&nodecount, sizeof(int), 0, (const sockaddr*)&sender, sizeof(sender));
for(UserList::iterator UserIterator=ClientList.begin();
UserIterator!=ClientList.end();
++UserIterator)
{
sendto(PrimaryUDP, (const char*)(*UserIterator), sizeof(stUserListNode), 0, (const sockaddr*)&sender, sizeof(sender));
}
break;
}
case LOGOUT:
{
// 將此客戶信息刪除
printf("has a user logout : %s\n", recvbuf.message.logoutmember.userName);
UserList::iterator removeiterator = NULL;
for(UserList::iterator UserIterator=ClientList.begin();
UserIterator!=ClientList.end();
++UserIterator)
{
if( strcmp( ((*UserIterator)->userName), recvbuf.message.logoutmember.userName) == 0 )
{
removeiterator = UserIterator;
break;
}
}
if(removeiterator != NULL)
ClientList.remove(*removeiterator);
break;
}
case P2PTRANS:
{
// 某個客戶希望服務端向另外一個客戶發送一個打洞消息
printf("%s wants to p2p %s\n",inet_ntoa(sender.sin_addr),recvbuf.message.translatemessage.userName);
stUserListNode node = GetUser(recvbuf.message.translatemessage.userName);
sockaddr_in remote;
remote.sin_family=AF_INET;
remote.sin_port= htons(node.port);
remote.sin_addr.s_addr = htonl(node.ip);
in_addr tmp;
tmp.S_un.S_addr = htonl(node.ip);
printf("the address is %s,and port is %d\n",inet_ntoa(tmp), node.port);
stP2PMessage transMessage;
transMessage.iMessageType = P2PSOMEONEWANTTOCALLYOU;
transMessage.iStringLen = ntohl(sender.sin_addr.S_un.S_addr);
transMessage.Port = ntohs(sender.sin_port);
sendto(PrimaryUDP,(const char*)&transMessage, sizeof(transMessage), 0, (const sockaddr *)&remote, sizeof(remote));
break;
}
case GETALLUSER:
{
int command = GETALLUSER;
sendto(PrimaryUDP, (const char*)&command, sizeof(int), 0, (const sockaddr*)&sender, sizeof(sender));
int nodecount = (int)ClientList.size();
sendto(PrimaryUDP, (const char*)&nodecount, sizeof(int), 0, (const sockaddr*)&sender, sizeof(sender));
for(UserList::iterator UserIterator=ClientList.begin();
UserIterator!=ClientList.end();
++UserIterator)
{
sendto(PrimaryUDP, (const char*)(*UserIterator), sizeof(stUserListNode), 0, (const sockaddr*)&sender, sizeof(sender));
}
break;
}
}
}
}
}
catch(Exception &e)
{
printf(e.GetMessage());
return 1;
}
return 0;
}
/* P2P 程序客戶端
*
* 文件名：P2PClient.c
*
* 日期：2004-5-21
*
* 作者：shootingstars(zhouhuis22@sina.com)
*
*/
#pragma comment(lib,"ws2_32.lib")
#include "windows.h"
#include "..\proto.h"
#include "..\Exception.h"
#include <iostream>
using namespace std;
UserList ClientList;
#define COMMANDMAXC 256
#define MAXRETRY 5
SOCKET PrimaryUDP;
char UserName[10];
char ServerIP[20];
bool RecvedACK;
void InitWinSock()
{
WSADATA wsaData;
if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
{
printf("Windows sockets 2.2 startup");
throw Exception("");
}
else{
printf("Using %s (Status: %s)\n",
wsaData.szDescription, wsaData.szSystemStatus);
printf("with API versions %d.%d to %d.%d\n\n",
LOBYTE(wsaData.wVersion), HIBYTE(wsaData.wVersion),
LOBYTE(wsaData.wHighVersion), HIBYTE(wsaData.wHighVersion));
}
}
SOCKET mksock(int type)
{
SOCKET sock = socket(AF_INET, type, 0);
if (sock < 0)
{
printf("create socket error");
throw Exception("");
}
return sock;
}
stUserListNode GetUser(char *username)
{
for(UserList::iterator UserIterator=ClientList.begin();
UserIterator!=ClientList.end();
++UserIterator)
{
if( strcmp( ((*UserIterator)->userName), username) == 0 )
return *(*UserIterator);
}
throw Exception("not find this user");
}
void BindSock(SOCKET sock)
{
sockaddr_in sin;
sin.sin_addr.S_un.S_addr = INADDR_ANY;
sin.sin_family = AF_INET;
sin.sin_port = 0;
if (bind(sock, (struct sockaddr*)&sin, sizeof(sin)) < 0)
throw Exception("bind error");
}
void ConnectToServer(SOCKET sock,char *username, char *serverip)
{
sockaddr_in remote;
remote.sin_addr.S_un.S_addr = inet_addr(serverip);
remote.sin_family = AF_INET;
remote.sin_port = htons(SERVER_PORT);
stMessage sendbuf;
sendbuf.iMessageType = LOGIN;
strncpy(sendbuf.message.loginmember.userName, username, 10);
sendto(sock, (const char*)&sendbuf, sizeof(sendbuf), 0, (const sockaddr*)&remote,sizeof(remote));
int usercount;
int fromlen = sizeof(remote);
int iread = recvfrom(sock, (char *)&usercount, sizeof(int), 0, (sockaddr *)&remote, &fromlen);
if(iread<=0)
{
throw Exception("Login error\n");
}
// 登錄到服務端后，接收服務端發來的已經登錄的用戶的信息
cout<<"Have "<<usercount<<" users logined server:"<<endl;
for(int i = 0;i<usercount;i++)
{
stUserListNode *node = new stUserListNode;
recvfrom(sock, (char*)node, sizeof(stUserListNode), 0, (sockaddr *)&remote, &fromlen);
ClientList.push_back(node);
cout<<"Username:"<<node->userName<<endl;
in_addr tmp;
tmp.S_un.S_addr = htonl(node->ip);
cout<<"UserIP:"<<inet_ntoa(tmp)<<endl;
cout<<"UserPort:"<<node->port<<endl;
cout<<""<<endl;
}
}
void OutputUsage()
{
cout<<"You can input you command:\n"
<<"Command Type:\"send\",\"exit\",\"getu\"\n"
<<"Example : send Username Message\n"
<<" exit\n"
<<" getu\n"
<<endl;
}
/* 這是主要的函數：發送一個消息給某個用戶(C)
*流程：直接向某個用戶的外網IP發送消息，如果此前沒有聯系過
* 那么此消息將無法發送，發送端等待超時。
* 超時后，發送端將發送一個請求信息到服務端，
* 要求服務端發送給客戶C一個請求，請求C給本機發送打洞消息
* 以上流程將重復MAXRETRY次
*/
bool SendMessageTo(char *UserName, char *Message)
{
char realmessage[256];
unsigned int UserIP;
unsigned short UserPort;
bool FindUser = false;
for(UserList::iterator UserIterator=ClientList.begin();
UserIterator!=ClientList.end();
++UserIterator)
{
if( strcmp( ((*UserIterator)->userName), UserName) == 0 )
{
UserIP = (*UserIterator)->ip;
UserPort = (*UserIterator)->port;
FindUser = true;
}
}
if(!FindUser)
return false;
strcpy(realmessage, Message);
for(int i=0;i<MAXRETRY;i++)
{
RecvedACK = false;
sockaddr_in remote;
remote.sin_addr.S_un.S_addr = htonl(UserIP);
remote.sin_family = AF_INET;
remote.sin_port = htons(UserPort);
stP2PMessage MessageHead;
MessageHead.iMessageType = P2PMESSAGE;
MessageHead.iStringLen = (int)strlen(realmessage)+1;
int isend = sendto(PrimaryUDP, (const char *)&MessageHead, sizeof(MessageHead), 0, (const sockaddr*)&remote, sizeof(remote));
isend = sendto(PrimaryUDP, (const char *)&realmessage, MessageHead.iStringLen, 0, (const sockaddr*)&remote, sizeof(remote));
// 等待接收線程將此標記修改
for(int j=0;j<10;j++)
{
if(RecvedACK)
return true;
else
Sleep(300);
}
// 沒有接收到目標主機的回應，認為目標主機的端口映射沒有
// 打開，那么發送請求信息給服務器，要服務器告訴目標主機
// 打開映射端口（UDP打洞）
sockaddr_in server;
server.sin_addr.S_un.S_addr = inet_addr(ServerIP);
server.sin_family = AF_INET;
server.sin_port = htons(SERVER_PORT);
stMessage transMessage;
transMessage.iMessageType = P2PTRANS;
strcpy(transMessage.message.translatemessage.userName, UserName);
sendto(PrimaryUDP, (const char*)&transMessage, sizeof(transMessage), 0, (const sockaddr*)&server, sizeof(server));
Sleep(100);// 等待對方先發送信息。
}
return false;
}
// 解析命令，暫時只有exit和send命令
// 新增getu命令，獲取當前服務器的所有用戶
void ParseCommand(char * CommandLine)
{
if(strlen(CommandLine)<4)
return;
char Command[10];
strncpy(Command, CommandLine, 4);
Command[4]='\0';
if(strcmp(Command,"exit")==0)
{
stMessage sendbuf;
sendbuf.iMessageType = LOGOUT;
strncpy(sendbuf.message.logoutmember.userName, UserName, 10);
sockaddr_in server;
server.sin_addr.S_un.S_addr = inet_addr(ServerIP);
server.sin_family = AF_INET;
server.sin_port = htons(SERVER_PORT);
sendto(PrimaryUDP,(const char*)&sendbuf, sizeof(sendbuf), 0, (const sockaddr *)&server, sizeof(server));
shutdown(PrimaryUDP, 2);
closesocket(PrimaryUDP);
exit(0);
}
else if(strcmp(Command,"send")==0)
{
char sendname[20];
char message[COMMANDMAXC];
int i;
for(i=5;;i++)
{
if(CommandLine[i]!=' ')
sendname[i-5]=CommandLine[i];
else
{
sendname[i-5]='\0';
break;
}
}
strcpy(message, &(CommandLine[i+1]));
if(SendMessageTo(sendname, message))
printf("Send OK!\n");
else
printf("Send Failure!\n");
}
else if(strcmp(Command,"getu")==0)
{
int command = GETALLUSER;
sockaddr_in server;
server.sin_addr.S_un.S_addr = inet_addr(ServerIP);
server.sin_family = AF_INET;
server.sin_port = htons(SERVER_PORT);
sendto(PrimaryUDP,(const char*)&command, sizeof(command), 0, (const sockaddr *)&server, sizeof(server));
}
}
// 接受消息線程
DWORD WINAPI RecvThreadProc(LPVOID lpParameter)
{
sockaddr_in remote;
int sinlen = sizeof(remote);
stP2PMessage recvbuf;
for(;;)
{
int iread = recvfrom(PrimaryUDP, (char *)&recvbuf, sizeof(recvbuf), 0, (sockaddr *)&remote, &sinlen);
if(iread<=0)
{
printf("recv error\n");
continue;
}
switch(recvbuf.iMessageType)
{
case P2PMESSAGE:
{
// 接收到P2P的消息
char *comemessage= new char[recvbuf.iStringLen];
int iread1 = recvfrom(PrimaryUDP, comemessage, 256, 0, (sockaddr *)&remote, &sinlen);
comemessage[iread1-1] = '\0';
if(iread1<=0)
throw Exception("Recv Message Error\n");
else
{
printf("Recv a Message:%s\n",comemessage);
stP2PMessage sendbuf;
sendbuf.iMessageType = P2PMESSAGEACK;
sendto(PrimaryUDP, (const char*)&sendbuf, sizeof(sendbuf), 0, (const sockaddr*)&remote, sizeof(remote));
}
delete []comemessage;
break;
}
case P2PSOMEONEWANTTOCALLYOU:
{
// 接收到打洞命令，向指定的IP地址打洞
printf("Recv p2someonewanttocallyou data\n");
sockaddr_in remote;
remote.sin_addr.S_un.S_addr = htonl(recvbuf.iStringLen);
remote.sin_family = AF_INET;
remote.sin_port = htons(recvbuf.Port);
// UDP hole punching
stP2PMessage message;
message.iMessageType = P2PTRASH;
sendto(PrimaryUDP, (const char *)&message, sizeof(message), 0, (const sockaddr*)&remote, sizeof(remote));
break;
}
case P2PMESSAGEACK:
{
// 發送消息的應答
RecvedACK = true;
break;
}
case P2PTRASH:
{
// 對方發送的打洞消息，忽略掉。
//do nothing 
printf("Recv p2ptrash data\n");
break;
}
case GETALLUSER:
{
int usercount;
int fromlen = sizeof(remote);
int iread = recvfrom(PrimaryUDP, (char *)&usercount, sizeof(int), 0, (sockaddr *)&remote, &fromlen);
if(iread<=0)
{
throw Exception("Login error\n");
}
ClientList.clear();
cout<<"Have "<<usercount<<" users logined server:"<<endl;
for(int i = 0;i<usercount;i++)
{
stUserListNode *node = new stUserListNode;
recvfrom(PrimaryUDP, (char*)node, sizeof(stUserListNode), 0, (sockaddr *)&remote, &fromlen);
ClientList.push_back(node);
cout<<"Username:"<<node->userName<<endl;
in_addr tmp;
tmp.S_un.S_addr = htonl(node->ip);
cout<<"UserIP:"<<inet_ntoa(tmp)<<endl;
cout<<"UserPort:"<<node->port<<endl;
cout<<""<<endl;
}
break;
}
}
}
}
int main(int argc, char* argv[])
{
try
{
InitWinSock();
PrimaryUDP = mksock(SOCK_DGRAM);
BindSock(PrimaryUDP);
cout<<"Please input server ip:";
cin>>ServerIP;
cout<<"Please input your name:";
cin>>UserName;
ConnectToServer(PrimaryUDP, UserName, ServerIP);
HANDLE threadhandle = CreateThread(NULL, 0, RecvThreadProc, NULL, NULL, NULL);
CloseHandle(threadhandle);
OutputUsage();
for(;;)
{
char Command[COMMANDMAXC];
gets(Command);
ParseCommand(Command);
}
}
catch(Exception &e)
{
printf(e.GetMessage());
return 1;
}
return 0;
}
/* 異常類
*
* 文件名：Exception.h
*
* 日期：2004.5.5
*
* 作者：shootingstars(zhouhuis22@sina.com)
*/
#ifndef __HZH_Exception__
#define __HZH_Exception__
#define EXCEPTION_MESSAGE_MAXLEN 256
#include "string.h"
class Exception
{
private:
char m_ExceptionMessage[EXCEPTION_MESSAGE_MAXLEN];
public:
Exception(char *msg)
{
strncpy(m_ExceptionMessage, msg, EXCEPTION_MESSAGE_MAXLEN);
}
char *GetMessage()
{
return m_ExceptionMessage;
}
};
#endif
/* P2P 程序傳輸協議
*
* 日期：2004-5-21
*
* 作者：shootingstars(zhouhuis22@sina.com)
*
*/
#pragma once
#include <list>
// 定義iMessageType的值
#define LOGIN 1
#define LOGOUT 2
#define P2PTRANS 3
#define GETALLUSER 4
// 服務器端口
#define SERVER_PORT 2280
// Client登錄時向服務器發送的消息
struct stLoginMessage
{
char userName[10];
char password[10];
};
// Client注銷時發送的消息
struct stLogoutMessage
{
char userName[10];
};
// Client向服務器請求另外一個Client(userName)向自己方向發送UDP打洞消息
struct stP2PTranslate
{
char userName[10];
};
// Client向服務器發送的消息格式
struct stMessage
{
int iMessageType;
union _message
{
stLoginMessage loginmember;
stLogoutMessage logoutmember;
stP2PTranslate translatemessage;
}message;
};
// 客戶節點信息
struct stUserListNode
{
char userName[10];
unsigned int ip;
unsigned short port;
};
// Server向Client發送的消息
struct stServerToClient
{
int iMessageType;
union _message
{
stUserListNode user;
}message;
};
//======================================
// 下面的協議用于客戶端之間的通信
//======================================
#define P2PMESSAGE 100 // 發送消息
#define P2PMESSAGEACK 101 // 收到消息的應答
#define P2PSOMEONEWANTTOCALLYOU 102 // 服務器向客戶端發送的消息
// 希望此客戶端發送一個UDP打洞包
#define P2PTRASH 103 // 客戶端發送的打洞包，接收端應該忽略此消息
// 客戶端之間發送消息格式
struct stP2PMessage
{
int iMessageType;
int iStringLen; // or IP address
unsigned short Port;
};
using namespace std;
typedef list<stUserListNode *> UserList;
C# 語言代碼
1． WellKnown公用庫
namespace P2P.WellKnown
{
using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
/// <summary>
/// P2PConsts 的摘要說明。
/// </summary>
public class P2PConsts
{
/// <summary>
/// 服務器偵聽端口號
/// </summary>
public const int SRV_PORT = 2280;
}
/// <summary>
/// User 的摘要說明。
/// </summary>
[Serializable]
public class User
{
protected string userName;
protected IPEndPoint netPoint;
public User(string UserName, IPEndPoint NetPoint)
{
this.userName = userName;
this.netPoint = NetPoint;
}
public string UserName
{
get { return userName; }
}
public IPEndPoint NetPoint
{
get { return netPoint; }
set { netPoint = value;}
}
}
/// <summary>
/// UserCollection 的摘要說明。
/// </summary>
[Serializable]
public class UserCollection : CollectionBase
{
public void Add(User user)
{
InnerList.Add(user);
}
public void Remove(User user)
{
InnerList.Remove(user);
}
public User this[int index]
{
get { return (User)InnerList[index]; }
}
public User Find(string userName)
{
foreach(User user in this)
{
if (string.Compare(userName, user.UserName, true) == 0)
{
return user;
}
}
return null;
}
}
/// <summary>
/// FormatterHelper 序列化，反序列化消息的幫助類
/// </summary>
public class FormatterHelper
{
public static byte[] Serialize(object obj)
{
BinaryFormatter binaryF = new BinaryFormatter();
MemoryStream ms = new MemoryStream(1024*10);
binaryF.Serialize(ms, obj);
ms.Seek(0, SeekOrigin.Begin);
byte[] buffer = new byte[(int)ms.Length];
ms.Read(buffer, 0, buffer.Length);
ms.Close();
return buffer;
}
public static object Deserialize(byte[] buffer)
{
BinaryFormatter binaryF = new BinaryFormatter();
MemoryStream ms = new MemoryStream(buffer, 0, buffer.Length, false);
object obj = binaryF.Deserialize(ms);
ms.Close();
return obj;
}
}
/// <summary>
/// Message base class
/// </summary>
[System.Serializable]
public abstract class MessageBase
{
}
// Message from Client to Server
namespace C2S
{
/// <summary>
/// 客戶端發送到服務器的消息基類
/// </summary>
public abstract class CSMessage : MessageBase
{
private string userName;
protected CSMessage(string anUserName)
{
userName = anUserName;
}
public string UserName
{
get { return userName; }
}
}
/// <summary>
/// 用戶登錄消息
/// </summary>
public class LoginMessage : CSMessage
{
private string password;
public LoginMessage(string userName, string password) : base(userName)
{
this.password = password;
}
public string Password
{
get { return password; }
}
}
/// <summary>
/// 用戶登出消息
/// </summary>
public class LogoutMessage : CSMessage
{
public LogoutMessage(string userName) : base(userName)
{}
}
/// <summary>
/// 請求用戶列表消息
/// </summary>
public class GetUsersMessage : CSMessage
{
public GetUsersMessage(string userName) : base(userName)
{}
}
/// <summary>
/// 請求Purch Hole消息
/// </summary>
public class TranslateMessage : CSMessage
{
protected string toUserName;
public TranslateMessage(string userName, string toUserName) : base(userName)
{
this.toUserName = toUserName;
}
public string ToUserName
{
get { return this.toUserName; }
}
}
}
// Message from server to the client
namespace S2C
{
/// <summary>
/// 服務器發送到客戶端消息基類
/// </summary>
public abstract class SCMessage : MessageBase
{}
/// <summary>
/// 請求用戶列表應答消息
/// </summary>
public class GetUsersResponseMessage : SCMessage
{
private UserCollection userList;
public GetUsersResponseMessage(UserCollection users)
{
this.userList = users;
}
public UserCollection UserList
{
get { return userList; }
}
}
/// <summary>
/// 轉發請求Purch Hole消息
/// </summary>
public class SomeOneCallYouMessage : SCMessage
{
protected System.Net.IPEndPoint remotePoint;
public SomeOneCallYouMessage(System.Net.IPEndPoint point)
{
this.remotePoint = point;
}
public System.Net.IPEndPoint RemotePoint
{
get { return remotePoint; }
}
}
}
// Message from peer to the peer
namespace P2P
{
/// <summary>
/// 點對點消息基類
/// </summary>
public abstract class PPMessage : MessageBase
{}
/// <summary>
/// 測試消息
/// </summary>
public class WorkMessage : PPMessage
{
private string message;
public WorkMessage(string msg)
{
message = msg;
}
public string Message
{
get { return message; }
}
}
/// <summary>
/// 測試應答消息
/// </summary>
public class ACKMessage : PPMessage
{
}
/// <summary>
/// P2P Purch Hole Message
/// </summary>
public class TrashMessage : PPMessage
{}
}
}
2． P2Pserver
namespace P2P.P2PServer
{
using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using P2P.WellKnown;
/// <summary>
/// AppClass 的摘要說明。
/// </summary>
public class AppClass
{
public static void Main()
{
Server server = new Server();
try
{
server.Start();
Console.ReadLine();
server.Stop();
}
catch
{
}
}
}
/// <summary>
/// Server 的摘要說明。
/// </summary>
public class Server
{
private UdpClient server;
private UserCollection userList;
private Thread serverThread;
private IPEndPoint remotePoint;
public Server()
{
userList = new UserCollection();
remotePoint = new IPEndPoint(IPAddress.Any, 0);
serverThread = new Thread(new ThreadStart(Run));
}
public void Start()
{
try
{
server = new UdpClient(P2PConsts.SRV_PORT);
serverThread.Start();
Console.WriteLine("P2P Server started, waiting client connect");
}
catch(Exception exp)
{
Console.WriteLine("Start P2P Server error: " + exp.Message);
throw exp;
}
}
public void Stop()
{
Console.WriteLine("P2P Server stopping");
try
{
serverThread.Abort();
server.Close();
Console.WriteLine("Stop OK.");
}
catch(Exception exp)
{
Console.WriteLine("Stop error: " + exp.Message);
throw exp;
}
}
private void Run()
{
byte[] buffer = null;
while (true)
{
byte[] msgBuffer = server.Receive(ref remotePoint);
try
{
object msgObj = FormatterHelper.Deserialize(msgBuffer);
Type msgType = msgObj.GetType();
if (msgType == typeof(P2P.WellKnown.C2S.LoginMessage))
{
// 轉換接受的消息
P2P.WellKnown.C2S.LoginMessage lginMsg = (P2P.WellKnown.C2S.LoginMessage)msgObj;
Console.WriteLine("has an user login: {0}", lginMsg.UserName);
// 添加用戶到列表
IPEndPoint userEndPoint = new IPEndPoint(remotePoint.Address, remotePoint.Port);
User user = new User(lginMsg.UserName, userEndPoint);
userList.Add(user);
// 發送應答消息
P2P.WellKnown.S2C.GetUsersResponseMessage usersMsg = new P2P.WellKnown.S2C.GetUsersResponseMessage(userList);
buffer = FormatterHelper.Serialize(usersMsg);
server.Send(buffer, buffer.Length, remotePoint);
}
else if (msgType == typeof(P2P.WellKnown.C2S.LogoutMessage))
{
// 轉換接受的消息
P2P.WellKnown.C2S.LogoutMessage lgoutMsg = (P2P.WellKnown.C2S.LogoutMessage)msgObj;
Console.WriteLine("has an user logout: {0}", lgoutMsg.UserName);
// 從列表中刪除用戶
User lgoutUser = userList.Find(lgoutMsg.UserName);
if (lgoutUser != null)
{
userList.Remove(lgoutUser);
}
}
else if (msgType == typeof(P2P.WellKnown.C2S.TranslateMessage))
{
// 轉換接受的消息
P2P.WellKnown.C2S.TranslateMessage transMsg = (P2P.WellKnown.C2S.TranslateMessage)msgObj;
Console.WriteLine("{0}(1) wants to p2p {2}", remotePoint.Address.ToString(), transMsg.UserName, transMsg.ToUserName);
// 獲取目標用戶
User toUser = userList.Find(transMsg.ToUserName);
// 轉發Purch Hole請求消息
if (toUser == null)
{
Console.WriteLine("Remote host {0} cannot be found at index server", transMsg.ToUserName);
}
else
{
P2P.WellKnown.S2C.SomeOneCallYouMessage transMsg2 = new P2P.WellKnown.S2C.SomeOneCallYouMessage(remotePoint);
buffer = FormatterHelper.Serialize(transMsg);
server.Send(buffer, buffer.Length, toUser.NetPoint);
}
}
else if (msgType == typeof(P2P.WellKnown.C2S.GetUsersMessage))
{
// 發送當前用戶信息到所有登錄客戶
P2P.WellKnown.S2C.GetUsersResponseMessage srvResMsg = new P2P.WellKnown.S2C.GetUsersResponseMessage(userList);
buffer = FormatterHelper.Serialize(srvResMsg);
foreach(User user in userList)
{
server.Send(buffer, buffer.Length, user.NetPoint);
}
}
Thread.Sleep(500);
}
catch{}
}
}
}
}
3． P2Pclient
namespace P2P.P2PClient
{
using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using P2P.WellKnown;
/// <summary>
/// AppClass 的摘要說明。
/// </summary>
public class AppClass
{
public static void Main()
{
Client client = new Client("202.96.134.103");
client.ConnectToServer("myname", "mypassword");
client.Start();
Console.WriteLine("test arguments");
while (true)
{
string str = Console.ReadLine();
client.PaserCommand(str);
}
}
}
/// <summary>
/// Client 的摘要說明。
/// </summary>
public class Client : IDisposable
{
private const int MAXRETRY = 10;
private UdpClient client;
private IPEndPoint hostPoint;
private IPEndPoint remotePoint;
private UserCollection userList;
private string myName;
private bool ReceivedACK;
private Thread listenThread;
public Client(string serverIP)
{
ReceivedACK = false;
remotePoint = new IPEndPoint(IPAddress.Any, 0);
hostPoint = new IPEndPoint(IPAddress.Parse(serverIP), P2PConsts.SRV_PORT);
client = new UdpClient();
userList = new UserCollection();
listenThread = new Thread(new ThreadStart(Run));
}
public void Start()
{
if (this.listenThread.ThreadState==ThreadState.Unstarted)
{
this.listenThread.Start();
Console.WriteLine("You can input you command: ");
Console.WriteLine("Command Type:"send","exit","getu"");
Console.WriteLine("Example : send Username Message");
Console.WriteLine(" exit");
Console.WriteLine(" getu");
}
}
public void ConnectToServer(string userName, string password)
{
myName = userName;
// 發送登錄消息到服務器
P2P.WellKnown.C2S.LoginMessage lginMsg = new P2P.WellKnown.C2S.LoginMessage(userName, password);
byte[] buffer = FormatterHelper.Serialize(lginMsg);
client.Send(buffer, buffer.Length, hostPoint);
// 接受服務器的登錄應答消息
buffer = client.Receive(ref remotePoint);
P2P.WellKnown.S2C.GetUsersResponseMessage srvResMsg = (P2P.WellKnown.S2C.GetUsersResponseMessage)FormatterHelper.Deserialize(buffer);
// 更新用戶列表
userList.Clear();
foreach(User user in srvResMsg.UserList)
{
userList.Add(user);
}
this.DisplayUsers(userList);
}
/// <summary>
/// 這是主要的函數：發送一個消息給某個用戶(C)
/// 流程：直接向某個用戶的外網IP發送消息，如果此前沒有聯系過
/// 那么此消息將無法發送，發送端等待超時。
/// 超時后，發送端將發送一個請求信息到服務端，要求服務端發送
/// 給客戶C一個請求，請求C給本機發送打洞消息
/// *以上流程將重復MAXRETRY次
/// </summary>
/// <param name="toUserName">對方用戶名</param>
/// <param name="message">待發送的消息</param>
/// <returns></returns>
private bool SendMessageTo(string toUserName, string message)
{
User toUser = userList.Find(toUserName);
if (toUser == null)
{
return false;
}
for (int i=0; i<MAXRETRY; i++)
{
P2P.WellKnown.P2P.WorkMessage workMsg = new P2P.WellKnown.P2P.WorkMessage(message);
byte[] buffer = FormatterHelper.Serialize(workMsg);
client.Send(buffer, buffer.Length, toUser.NetPoint);
// 等待接收線程將標記修改
for (int j=0; j<10; j++)
{
if (this.ReceivedACK)
{
this.ReceivedACK = false;
return true;
}
else
{
Thread.Sleep(300);
}
}
// 沒有接收到目標主機的回應，認為目標主機的端口映射沒有
// 打開，那么發送請求信息給服務器，要服務器告訴目標主機
// 打開映射端口（UDP打洞）
P2P.WellKnown.C2S.TranslateMessage transMsg = new P2P.WellKnown.C2S.TranslateMessage(myName, toUserName);
buffer = FormatterHelper.Serialize(transMsg);
client.Send(buffer, buffer.Length, hostPoint);
// 等待對方先發送信息
Thread.Sleep(100);
}
return false;
}
public void PaserCommand(string cmdstring)
{
cmdstring = cmdstring.Trim();
string[] args = cmdstring.Split(new char[]{' '});
if (args.Length > 0)
{
if (string.Compare(args[0], "exit", true) == 0)
{
P2P.WellKnown.C2S.LogoutMessage lgoutMsg = new P2P.WellKnown.C2S.LogoutMessage(myName);
byte[] buffer = FormatterHelper.Serialize(lgoutMsg);
client.Send(buffer, buffer.Length, hostPoint);
// do clear something here
Dispose();
System.Environment.Exit(0);
}
else if (string.Compare(args[0], "send", true) == 0)
{
if (args.Length > 2)
{
string toUserName = args[1];
string message = "";
for(int i=2; i<args.Length; i++)
{
if (args[i] == "") message += " ";
else message += args[i];
}
if (this.SendMessageTo(toUserName, message))
{
Console.WriteLine("Send OK!");
}
else
Console.WriteLine("Send Failed!");
}
}
else if (string.Compare(args[0], "getu", true) == 0)
{
P2P.WellKnown.C2S.GetUsersMessage getUserMsg = new P2P.WellKnown.C2S.GetUsersMessage(myName);
byte[] buffer = FormatterHelper.Serialize(getUserMsg);
client.Send(buffer, buffer.Length, hostPoint);
}
else
{
Console.WriteLine("Unknown command {0}", cmdstring);
}
}
}
private void DisplayUsers(UserCollection users)
{
foreach (User user in users)
{
Console.WriteLine("Username: {0}, IP:{1}, Port:{2}", user.UserName, user.NetPoint.Address.ToString(), user.NetPoint.Port);
}
}
private void Run()
{
byte[] buffer;
while (true)
{
buffer = client.Receive(ref remotePoint);
object msgObj = FormatterHelper.Deserialize(buffer);
Type msgType = msgObj.GetType();
if (msgType == typeof(P2P.WellKnown.S2C.GetUsersResponseMessage))
{
// 轉換消息
P2P.WellKnown.S2C.GetUsersResponseMessage usersMsg = (P2P.WellKnown.S2C.GetUsersResponseMessage)msgObj;
// 更新用戶列表
userList.Clear();
foreach(User user in usersMsg.UserList)
{
userList.Add(user);
}
this.DisplayUsers(userList);
}
else if (msgType == typeof(P2P.WellKnown.S2C.SomeOneCallYouMessage))
{
// 轉換消息
P2P.WellKnown.S2C.SomeOneCallYouMessage purchReqMsg = (P2P.WellKnown.S2C.SomeOneCallYouMessage)msgObj;
// 發送打洞消息到遠程主機
P2P.WellKnown.P2P.TrashMessage trashMsg = new P2P.WellKnown.P2P.TrashMessage();
buffer = FormatterHelper.Serialize(trashMsg);
client.Send(buffer, buffer.Length, purchReqMsg.RemotePoint);
}
else if (msgType == typeof(P2P.WellKnown.P2P.WorkMessage))
{
// 轉換消息
P2P.WellKnown.P2P.WorkMessage workMsg = (P2P.WellKnown.P2P.WorkMessage)msgObj;
Console.WriteLine("Receive a message: {0}", workMsg.Message);
// 發送應答消息
P2P.WellKnown.P2P.ACKMessage ackMsg = new P2P.WellKnown.P2P.ACKMessage();
buffer = FormatterHelper.Serialize(ackMsg);
client.Send(buffer, buffer.Length, remotePoint);
}
else if (msgType == typeof(P2P.WellKnown.P2P.ACKMessage))
{
this.ReceivedACK = true;
}
else if (msgType == typeof(P2P.WellKnown.P2P.TrashMessage))
{
Console.WriteLine("Recieve a trash message");
}
Thread.Sleep(100);
}
}
#region IDisposable 成員
public void Dispose()
{
try
{
this.listenThread.Abort();
this.client.Close();
}
catch
{}
}
#endregion
}
}
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