p2p学习记录

/* P2P 程序服务端
 * 
 * 文件名：P2PServer.c
 *
 * 日期：2004-5-21
 *
 * 作者：shootingstars([email protected])
 *
 */
#pragma comment(lib, "ws2_32.lib")

#include "windows.h"
#include "..\proto.h"
#include "..\Exception.h"

UserList ClientList;

void InitWinSock()//自定义初始化函数，套接字服务初始化，任何一个进程使用套接字服务时必须有的操作
{
	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);////自定义套接字创建函数，创建套接字,AF_INNET（使用IPV4地址），type（套接字类型，p2p一般使用udp），指定的协议类型（0代表默认），正常执行会返回套接字地址
	if (sock < 0)
	{
        printf("create socket error");
		throw Exception("");
	}
	return sock;
}

stUserListNode GetUser(char *username)//链表查找用户名，存在返回节点指针
{
	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);//SOCK_DGRAM udp套接字类型

		sockaddr_in local;//
		local.sin_family=AF_INET;
		local.sin_port= htons(SERVER_PORT); 
		local.sin_addr.s_addr = htonl(INADDR_ANY);//套接字地址初始化,INADDR_ANY代表本机地址
		int nResult=bind(PrimaryUDP,(sockaddr*)&local,sizeof(sockaddr));//PrimaryUDP套接字唯一标示，local的地址结构由它的地址类型决定sockaddr_in对应IPV4，最后一个参数是地址长度
		if(nResult==SOCKET_ERROR)
			throw Exception("bind error");

		sockaddr_in sender;//sender用于接收client登陆的用户地址信息，用于存储服务端发送消息的目标地址
		stMessage recvbuf;//定义cilent发送数据的格式，意味着服务器和客户端支持同一种协议，p2p使用私有协议
		memset(&recvbuf,0,sizeof(stMessage));

		// 开始主循环.
		// 主循环负责下面几件事情:
		// 一:读取客户端登陆和登出消息,记录客户列表
		// 二:转发客户p2p请求
		for(;;)
		{
			int dwSender = sizeof(sender);
			int ret = recvfrom(PrimaryUDP, (char *)&recvbuf, sizeof(stMessage), 0, (sockaddr *)&sender, &dwSender);//循环接收对应端口的信息，客户端使用事先定义的端口进行登入登出 p2p请求
			if(ret <= 0)
			{
				printf("recv error");
				continue;
			}
			else
			{
				int messageType = recvbuf.iMessageType;
				switch(messageType){
				case LOGIN:
					{
						//  将这个用户的信息记录到用户列表中
						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);

						// 发送已经登陆的客户信息
						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)); 
						}//将所有在线用户的信息发送给新登陆的client

						break;
					}
				case LOGOUT:
					{
						// 将此客户信息删除
						printf("has a user logout : %s\n", recvbuf.message.logoutmember.userName);
						UserList::iterator removeiterator = ClientList.begin();
						int flag = 1;
						for(UserList::iterator UserIterator=ClientList.begin();
							UserIterator!=ClientList.end();
							++UserIterator)
						{
							if( strcmp( ((*UserIterator)->userName), recvbuf.message.logoutmember.userName) == 0 )
							{
								removeiterator = UserIterator;
								flag = 0;
								break;
							}
						}
						if(flag==0&&(removeiterator!=ClientList.begin()))//46995
							ClientList.remove(*removeiterator);//移除用户信息
						break;
					}
				case P2PTRANS:
					{
						// 某个客户希望服务端向另外一个客户发送一个打洞消息
						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);//通过查找client消息结构体里存在的传输用户名，获取相应的地址和端口信息

						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);//将请求p2p通信的客户端的公网ip，端口至于发送buf中
                        
						sendto(PrimaryUDP,(const char*)&transMessage, sizeof(transMessage), 0, (const sockaddr *)&remote, sizeof(remote));//告知被请求p2p通信的客户端向对应地址端口的client发送udp打洞包

						break;
					}
				
				case GETALLUSER:
					{
						int command = GETALLUSER;
						sendto(PrimaryUDP, (const char*)&command, sizeof(int), 0, (const sockaddr*)&sender, sizeof(sender));//查询所有用户请求响应

						int nodecount = (int)ClientList.size();
						sendto(PrimaryUDP, (const char*)&nodecount, sizeof(int), 0, (const sockaddr*)&sender, sizeof(sender));//发送所有在线用户数目

						for(UserList::iterator UserIterator=ClientList.begin();
								UserIterator!=ClientList.end();
								++UserIterator)
						{
							sendto(PrimaryUDP, (const char*)(*UserIterator), sizeof(stUserListNode), 0, (const sockaddr*)&sender, sizeof(sender)); //遍历，循环发送所有用户信息
						}
						break;
					}
				}
			}
		}

	}
	catch(Exception &e)//捕获异常，发生异常就执行下面的语句
	{
		printf(e.GetMessage());
		return 1;
	}

	return 0;
}

转自：http://www.ppcn.net/p2ptech.html