MFC(线程同步与异步套接字,孙鑫C++第十六讲笔记整理)

1.事件对象：来实现线程的同步。与互斥对象一样均属于内核对象。

 当人工重置有信号时，所有线程均得到信号，所以不能设为人工重置。代码就不贴了，通过创建匿名的事件对象，也可以让一个程序只能运行一个实例。

 

 

2.关键代码段实现线程的同步：类似公用电话亭，只有当电话亭里面没人了，其它人才可以再进去打电话。用了4个函数，这种方法比较简单！但缺点是如果使用了多少关键代码码，容易赞成线程的死锁

 

 

3.线程死锁，用关键代码示例，用了两个临界区对象，实战中要注意避免这种错误！

 

 

4.使用异步套接字编写网络聊天室

 1)加载套接字库，进行版本协商，包含头文件，链接库文件，这次请示的是2.2版本！

 2）在类CChatDlg中增加一个成员变量m_socket,在析构函数中释放这个变量

 3）利用WSASocket()创建套接字（数据报类型的UDP型的）

 4）然后调用WSAAsyncSelect(m_socket,m_hWnd,UM_SOCK,FD_READ)为网络事件定义消息！此时如果发生FD_READ消息，系统会发送UM_SOCK消息给应用程序！程序并不会阻塞在这儿了！

 以上是在BOOL CChatDlg::OnInitDialog()完成

 5）然后完成消息响应！

 头文件中：#define UM_SOCK WM_USER+1

 afx_msg void OnSock(WPARAM,LPARAM);

  源文件中：

   ON_MESSAGE(UM_SOCK,OnSock)

   实现消息响应函数：void CChatDlg::OnSock(WPARAM wParam,LPARAM lParam)

{

 switch(LOWORD(lParam))

 {

 case FD_READ:

 WSABUF wsabuf;

 wsabuf.buf=new char[200];

 wsabuf.len=200;

 DWORD dwRead;

 DWORD dwFlag=0;

 SOCKADDR_IN addrFrom;

 int len=sizeof(SOCKADDR);

 CString str;

 CString strTemp;

 HOSTENT *pHost;

 if(SOCKET_ERROR==WSARecvFrom(m_socket,&wsabuf,1,&dwRead,&dwFlag,

     (SOCKADDR*)&addrFrom,&len,NULL,NULL))

 {

  MessageBox("接收数据失败！");

  return;

 }

 pHost=gethostbyaddr((char*)&addrFrom.sin_addr.S_un.S_addr,4,AF_INET);

 //str.Format("%s说 :%s",inet_ntoa(addrFrom.sin_addr),wsabuf.buf);

 str.Format("%s说 :%s",pHost->h_name,wsabuf.buf);

 str+="\r\n";

 GetDlgItemText(IDC_EDIT_RECV,strTemp);

 str+=strTemp;

 SetDlgItemText(IDC_EDIT_RECV,str);

 break;

 }

}

OK！

 6）完成数据发送的功能！

     void CChatDlg::OnBtnSend()

{

 // TOD Add your control notification handler code here

 DWORD dwIP;

 CString strSend;

 WSABUF wsabuf;

 DWORD dwSend;

 int len;

 CString strHostName;

 SOCKADDR_IN addrTo;

 HOSTENT* pHost;

 if(GetDlgItemText(IDC_EDIT_HOSTNAME,strHostName),strHostName=="")

 {

 ((CIPAddressCtrl*)GetDlgItem(IDC_IPADDRESS1))->GetAddress(dwIP);

 addrTo.sin_addr.S_un.S_addr=htonl(dwIP);

 }

 else

 {

 pHost=gethostbyname(strHostName);

 addrTo.sin_addr.S_un.S_addr=*((DWORD*)pHost->h_addr_list[0]);

 }

 

 addrTo.sin_family=AF_INET;

 addrTo.sin_port=htons(6000); GetDlgItemText(IDC_EDIT_SEND,strSend);

 len=strSend.GetLength();

 wsabuf.buf=strSend.GetBuffer(len);

 wsabuf.len=len+1; SetDlgItemText(IDC_EDIT_SEND,""); if(SOCKET_ERROR==WSASendTo(m_socket,&wsabuf,1,&dwSend,0,

  (SOCKADDR*)&addrTo,sizeof(SOCKADDR),NULL,NULL))

 {

 MessageBox("发送数据失败！");

 return;

 }

 

}     7）完成将主机名转换为IP地址的功能，以前将IP地址转换为主机名的功能，单线程的聊天室创建完毕！性能并且非常出色！

 

下面是一些具体的代码：

#include<windows.h>#include<iostream.h>DWORD WINAPI ThreadProc1( LPVOID lpParameter  );DWORD WINAPI ThreadProc2( LPVOID lpParameter   );int tickes=100;HANDLE hEvent;int main(){HANDLE hThread1=CreateThread(NULL,0,ThreadProc1,NULL,0,NULL);HANDLE hThread2=CreateThread(NULL,0,ThreadProc2,NULL,0,NULL);hEvent=CreateEvent(NULL,FALSE,TRUE,NULL);//自动，有信号CloseHandle(hThread1);CloseHandle(hThread2);Sleep(4000);return 0;}DWORD WINAPI ThreadProc1( LPVOID lpParameter   // thread data ){while(TRUE){SetEvent(hEvent);WaitForSingleObject(hEvent,INFINITE);if(tickes>0){cout<<"thread1 sell ticke: "<<tickes--<<endl;}else{break;}//ReleaseMutex(hEvent);ResetEvent(hEvent);}return 0;}DWORD WINAPI ThreadProc2( LPVOID lpParameter   // thread data ){while(TRUE){SetEvent(hEvent);WaitForSingleObject(hEvent,INFINITE);if(tickes>0){cout<<"thread2 sell ticke: "<<tickes--<<endl;}else{break;}//ReleaseMutex(hEvent);ResetEvent(hEvent);}return 0;}

 

//CreateEvent设置自定的，并且初始有信号/*#include<windows.h>#include<iostream.h>DWORD WINAPI ThreadProc1( LPVOID lpParameter  );DWORD WINAPI ThreadProc2( LPVOID lpParameter   );int tickes=100;HANDLE hEvent;int main(){HANDLE hThread1=CreateThread(NULL,0,ThreadProc1,NULL,0,NULL);HANDLE hThread2=CreateThread(NULL,0,ThreadProc2,NULL,0,NULL);hEvent=CreateEvent(NULL,FALSE,TRUE,NULL);//自动，有信号CloseHandle(hThread1);CloseHandle(hThread2);Sleep(4000);return 0;}DWORD WINAPI ThreadProc1( LPVOID lpParameter   // thread data ){while(TRUE){WaitForSingleObject(hEvent,INFINITE);if(tickes>0){cout<<"thread1 sell ticke: "<<tickes--<<endl;}else{break;}}return 0;}DWORD WINAPI ThreadProc2( LPVOID lpParameter   // thread data ){while(TRUE){WaitForSingleObject(hEvent,INFINITE);if(tickes>0){cout<<"thread2 sell ticke: "<<tickes--<<endl;}else{break;}}return 0;}*///结论是，设置自动的，并且开始有信号(无信号可以调用SetEvent来使无信号到有信号的一个转变)//只有一个线程获得了信号，并且运行完后(时间片到了)，则下一个线程是无法运行的，因为此时只有一个//线程有信号，并且运行完后，马上使得事件对象无信号

 

//CreateEvent手动，一开始就无信号/*#include<windows.h>#include<iostream.h>DWORD WINAPI ThreadProc1( LPVOID lpParameter  );DWORD WINAPI ThreadProc2( LPVOID lpParameter   );int tickes=100;HANDLE hEvent;int main(){HANDLE hThread1=CreateThread(NULL,0,ThreadProc1,NULL,0,NULL);HANDLE hThread2=CreateThread(NULL,0,ThreadProc2,NULL,0,NULL);hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);//手动，无信号SetEvent(hEvent);CloseHandle(hThread1);CloseHandle(hThread2);Sleep(4000);return 0;}DWORD WINAPI ThreadProc1( LPVOID lpParameter   // thread data ){while(TRUE){WaitForSingleObject(hEvent,INFINITE);if(tickes>0){cout<<"thread1 sell ticke: "<<tickes--<<endl;}else{break;}}return 0;}DWORD WINAPI ThreadProc2( LPVOID lpParameter   // thread data ){while(TRUE){WaitForSingleObject(hEvent,INFINITE);if(tickes>0){cout<<"thread2 sell ticke: "<<tickes--<<endl;}else{break;}}return 0;}*///使用手动设置，则任何线程都获得了信号，都可以运行,可以使用ResetEvent使得信号变得无效

 

//关键代码段，临界区域//如果只是Enter了但是没有Leave则下一个线程获取不了信号，下一个线程得不到执行/*#include<windows.h>#include<iostream.h>DWORD WINAPI ThreadProc1( LPVOID lpParameter  );DWORD WINAPI ThreadProc2( LPVOID lpParameter   );int tickes=100;CRITICAL_SECTION section;int main(){HANDLE hThread1=CreateThread(NULL,0,ThreadProc1,NULL,0,NULL);HANDLE hThread2=CreateThread(NULL,0,ThreadProc2,NULL,0,NULL);CloseHandle(hThread1);CloseHandle(hThread2);InitializeCriticalSection(§ion);Sleep(4000);DeleteCriticalSection(§ion);return 0;}DWORD WINAPI ThreadProc1( LPVOID lpParameter   // thread data ){while(TRUE){EnterCriticalSection(§ion);if(tickes>0){cout<<"thread1 sell ticke: "<<tickes--<<endl;}else{break;}LeaveCriticalSection(§ion);}return 0;}DWORD WINAPI ThreadProc2( LPVOID lpParameter   // thread data ){while(TRUE){EnterCriticalSection(§ion);if(tickes>0){cout<<"thread2 sell ticke: "<<tickes--<<endl;}else{break;}LeaveCriticalSection(§ion);}return 0;}*/

 

//死锁的体现/*#include<windows.h>#include<iostream.h>DWORD WINAPI ThreadProc1( LPVOID lpParameter  );DWORD WINAPI ThreadProc2( LPVOID lpParameter   );int tickes=100;CRITICAL_SECTION sectionA;CRITICAL_SECTION sectionB;int main(){HANDLE hThread1=CreateThread(NULL,0,ThreadProc1,NULL,0,NULL);HANDLE hThread2=CreateThread(NULL,0,ThreadProc2,NULL,0,NULL);CloseHandle(hThread1);CloseHandle(hThread2);InitializeCriticalSection(§ionA);InitializeCriticalSection(§ionB);Sleep(4000);DeleteCriticalSection(§ionB);DeleteCriticalSection(§ionA);return 0;}DWORD WINAPI ThreadProc1( LPVOID lpParameter   // thread data ){while(TRUE){EnterCriticalSection(§ionA);Sleep(1);EnterCriticalSection(§ionB);if(tickes>0){cout<<"thread1 sell ticke: "<<tickes--<<endl;}else{break;}LeaveCriticalSection(§ionB);LeaveCriticalSection(§ionA);}return 0;}DWORD WINAPI ThreadProc2( LPVOID lpParameter   // thread data ){while(TRUE){EnterCriticalSection(§ionB);Sleep(1);EnterCriticalSection(§ionA);if(tickes>0){cout<<"thread2 sell ticke: "<<tickes--<<endl;}else{break;}LeaveCriticalSection(§ionA);LeaveCriticalSection(§ionB);}return 0;}*/

 

 

下面是用异步套接字写的聊天程序,跟前面的多线程对比一下：

1新建一个基于单文档的MFC程序

2拉控件成这样：

 

3在CXXAPP文件中的InitInstance中添加WSAStartupXX库添加函数，查看MSDN的WSAStartup

4在CXXDlg中添加成员变量SOCKET m_socket和成员函数 InitSocket;

BOOL CNewChatDlg::InitSocket(){m_socket=WSASocket(AF_INET,SOCK_DGRAM,0,NULL,0,0);if(!m_socket){AfxMessageBox("创建套接字失败");return FALSE;}SOCKADDR_IN sockaddr;sockaddr.sin_addr.S_un.S_addr=htonl(INADDR_ANY);sockaddr.sin_family=AF_INET;sockaddr.sin_port=htons(6000);int returnbind;returnbind=bind(m_socket,(SOCKADDR*)&sockaddr,sizeof(SOCKADDR));if(SOCKET_ERROR==returnbind){AfxMessageBox("绑定失败");return FALSE;}int se;se=WSAAsyncSelect(m_socket,m_hWnd,WM_RECV,FD_READ);if(SOCKET_ERROR==se){AfxMessageBox("创建网络读取时间失败");return FALSE;}return TRUE;}

并在CXXDlg中的OnInitDialog中调用InitSocket();

5自定义消息响应事件

a #define WM_RECV WM_USER+1

b afx_msg void OnRecv(WPARAM wParam,LPARAM lParam);

c ON_MESSAGE(WM_RECV,OnRecv)

d 

void CNewChatDlg::OnRecv(WPARAM wParam,LPARAM lParam){switch(LOWORD(lParam)){case FD_READ:WSABUF wsabuf;wsabuf.buf=new char[200];wsabuf.len=200;DWORD dwread;DWORD dwflag=0;SOCKADDR_IN sockaddr;int len=sizeof(SOCKADDR);if(SOCKET_ERROR ==WSARecvFrom(m_socket,&wsabuf,1,&dwread,&dwflag,(SOCKADDR*)&sockaddr,&len,NULL,NULL)){AfxMessageBox("接收数据失败");return ;}char temp[200];sprintf(temp,"%s 说 %s ",inet_ntoa(sockaddr.sin_addr),wsabuf.buf);CString jieshou;GetDlgItemText(ID_JIESHOU,jieshou);if(jieshou!=""){jieshou+="\r\n";}jieshou+=temp;SetDlgItemText(ID_JIESHOU,jieshou);break;}}

6添加发送按钮事件：

void CNewChatDlg::OnSend() {// TODO: Add your control notification handler code hereDWORD dwIp;CString strsend;((CIPAddressCtrl*)GetDlgItem(ID_IPADDRESS))->GetAddress(dwIp);SOCKADDR_IN sockaddr;sockaddr.sin_addr.S_un.S_addr=htonl(dwIp);sockaddr.sin_family=AF_INET;sockaddr.sin_port=htons(6000);GetDlgItemText(ID_FASONG,strsend);WSABUF wsabuf;wsabuf.buf=strsend.GetBuffer(strsend.GetLength());wsabuf.len=strsend.GetLength()+1;SetDlgItemText(ID_FASONG,"");DWORD dwsent;int len=sizeof(SOCKADDR);if(SOCKET_ERROR ==WSASendTo(m_socket,&wsabuf,1,&dwsent,0,(SOCKADDR*)&sockaddr,len,NULL,NULL)){AfxMessageBox("发送数据失败");return ;}}CNewChatDlg::~CNewChatDlg(){closesocket(m_socket);}

 

CNewChatDlg::~CNewChatDlg(){closesocket(m_socket);}

 

要熟悉异步套接字和多线程的编程，这个很重要，一定要熟练。