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;}*/
