深入分析驴子系列（1）
一直在看驴子的代码，网上进行深入分析的文章不多，也许 这和驴子的代码量太大，代码质量不高也许有关系。但更多的也许是不想分享，舍不得分享。其实，它本身就是开源的 不分享人家慢慢看也能看懂 。由于时间关系 我会陆续把分析的文章帖上来，与各位网友分享，也希望大家拍砖 进行讨论 也把你的心得分享出来。。系列分析文章如果没有特别注明 以easy mule 0.47为准
CListenSocket 类 的作用就是 监听 等待客户端的socket 到来 并维护到来的套接字 把accept进来的套接字 加入到list 中
// 该函数的作用是创建本地的listensocket, 是否Accept 连接是由winsock消息驱动
bool CListenSocket::StartListening()
{
bListening = true;
// Creating the socket with SO_REUSEADDR may solve LowID issues if emule was restarted
// quickly or started after a crash, but(!) it will also create another problem. If the
// socket is already used by some other application (e.g. a 2nd emule), we though bind
// to that socket leading to the situation that 2 applications are listening at the same
// port!
if (!Create(thePrefs.GetPort(), SOCK_STREAM, FD_ACCEPT, thePrefs.GetBindAddrA(), FALSE/*bReuseAddr*/))
return false;
if (!Listen())
return false;
m_port = thePrefs.GetPort();
return true;
}
// 该函数改名为RestartAccept 更合适
// 它的本意是重新开始接受连接
// 为什么需要重新开始接受连接呢，原因是连接数过多情况下，
// 会暂时StopListeing (bListening 设置为false;) ，
// 连接数少的情况下会重新开始接受连接RestartListening；
// 应该注意的是：这个暂停和重新开始并不实际关闭/打开本地listen端口，只是设置一个bool标志
void CListenSocket::ReStartListening()
{
bListening = true;
ASSERT( m_nPendingConnections >= 0 );
if (m_nPendingConnections > 0)
{
m_nPendingConnections--;
OnAccept(0);
}
}
连接到来
void CListenSocket::OnAccept(int nErrorCode)
{
if (!nErrorCode) //先判断是否有错误
{
m_nPendingConnections++;
if (m_nPendingConnections < 1)
{
ASSERT(0);
m_nPendingConnections = 1;
}
if (TooManySockets(true) && !theApp.serverconnect->IsConnecting()) //如果已经连接的套接字过多 或者 连接断开
{ // 则停止监听返回
StopListening();
return;
}
else if (!bListening)
ReStartListening(); //If the client is still at maxconnections, this will allow it to go above it.. But if you don't, you will get a lowID on all servers.
uint32 nFataErrors = 0;
while (m_nPendingConnections > 0)
{
m_nPendingConnections--;
CClientReqSocket* newclient;
SOCKADDR_IN SockAddr = {0};
int iSockAddrLen = sizeof SockAddr;
if (thePrefs.GetConditionalTCPAccept() && !thePrefs.GetProxySettings().UseProxy)
{
_iAcceptConnectionCondRejected = 0;
SOCKET sNew = WSAAccept(m_SocketData.hSocket, (SOCKADDR*)&SockAddr, &iSockAddrLen, AcceptConnectionCond, 0); // 这是调用API接受连接
if (sNew == INVALID_SOCKET)
{
DWORD nError = GetLastError(); // 根据返回的异常进行处理
if (nError == WSAEWOULDBLOCK)
{
DebugLogError(LOG_STATUSBAR, _T("%hs: Backlogcounter says %u connections waiting, Accept() says WSAEWOULDBLOCK - setting counter to zero!"), __FUNCTION__, m_nPendingConnections);
m_nPendingConnections = 0;
break;
}
else
{
if (nError != WSAECONNREFUSED || _iAcceptConnectionCondRejected == 0){
DebugLogError(LOG_STATUSBAR, _T("%hs: Backlogcounter says %u connections waiting, Accept() says %s - setting counter to zero!"), __FUNCTION__, m_nPendingConnections, GetErrorMessage(nError, 1));
nFataErrors++;
}
else if (_iAcceptConnectionCondRejected == 1)
theStats.filteredclients++;
}
if (nFataErrors > 10)
{
// the question is what todo on a error. We cant just ignore it because then the backlog will fill up
// and lock everything. We can also just endlos try to repeat it because this will lock up eMule
// this should basically never happen anyway
// however if we are in such a position, try to reinitalize the socket.
DebugLogError(LOG_STATUSBAR, _T("%hs: Accept() Error Loop, recreating socket"), __FUNCTION__);
Close();
StartListening();
m_nPendingConnections = 0;
break;
}
continue;
}
newclient = new CClientReqSocket; // 一个新的套接字
VERIFY( newclient->InitAsyncSocketExInstance() );
newclient->m_SocketData.hSocket = sNew;
newclient->AttachHandle(sNew);
AddConnection();
}
else
{
newclient = new CClientReqSocket;
if (!Accept(*newclient, (SOCKADDR*)&SockAddr, &iSockAddrLen))
{
newclient->Safe_Delete();
DWORD nError = GetLastError();
if (nError == WSAEWOULDBLOCK)
{
DebugLogError(LOG_STATUSBAR, _T("%hs: Backlogcounter says %u connections waiting, Accept() says WSAEWOULDBLOCK - setting counter to zero!"), __FUNCTION__, m_nPendingConnections);
m_nPendingConnections = 0;
break;
}
else
{
DebugLogError(LOG_STATUSBAR, _T("%hs: Backlogcounter says %u connections waiting, Accept() says %s - setting counter to zero!"), __FUNCTION__, m_nPendingConnections, GetErrorMessage(nError, 1));
nFataErrors++;
}
if (nFataErrors > 10){
// the question is what todo on a error. We cant just ignore it because then the backlog will fill up
// and lock everything. We can also just endlos try to repeat it because this will lock up eMule
// this should basically never happen anyway
// however if we are in such a position, try to reinitalize the socket.
DebugLogError(LOG_STATUSBAR, _T("%hs: Accept() Error Loop, recreating socket"), __FUNCTION__);
Close();
StartListening();
m_nPendingConnections = 0;
break;
}
continue;
}
AddConnection();
if (SockAddr.sin_addr.S_un.S_addr == 0) // for safety..
{
iSockAddrLen = sizeof SockAddr;
newclient->GetPeerName((SOCKADDR*)&SockAddr, &iSockAddrLen);
DebugLogWarning(_T("SockAddr.sin_addr.S_un.S_addr == 0; GetPeerName returned %s"), ipstr(SockAddr.sin_addr.S_un.S_addr));
}
ASSERT( SockAddr.sin_addr.S_un.S_addr != 0 && SockAddr.sin_addr.S_un.S_addr != INADDR_NONE );
if (theApp.ipfilter->IsFiltered(SockAddr.sin_addr.S_un.S_addr))
{
if (thePrefs.GetLogFilteredIPs())
AddDebugLogLine(false, _T("Rejecting connection attempt (IP=%s) - IP filter (%s)"), ipstr(SockAddr.sin_addr.S_un.S_addr), theApp.ipfilter->GetLastHit());
newclient->Safe_Delete();
theStats.filteredclients++;
continue;
}
if (theApp.clientlist->IsBannedClient(SockAddr.sin_addr.S_un.S_addr))
{
if (thePrefs.GetLogBannedClients())
{
CUpDownClient* pClient = theApp.clientlist->FindClientByIP(SockAddr.sin_addr.S_un.S_addr);
AddDebugLogLine(false, _T("Rejecting connection attempt of banned client %s %s"), ipstr(SockAddr.sin_addr.S_un.S_addr), pClient->DbgGetClientInfo());
}
newclient->Safe_Delete();
continue;
}
}
newclient->AsyncSelect(FD_WRITE | FD_READ | FD_CLOSE);
}
ASSERT( m_nPendingConnections >= 0 );
}
}
以上就是这个类的 主要函数 剩下的都比较简单，就不再。。。
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