《windows網絡編程技術》之 Winsock I/O方法（1）
select模型：
select函數原型
int select(
int nfds,
fd_set FAR * readfds,
fd_set FAR * writefds,
fd_set FAR * exceptfds,
const struct timeval FAR * timeout
);
nfds為了保持與早期兼容，可忽略。
fd_set，代表一系列特定的套接字的集合，readset用于檢查可讀性，writeset用于檢查可寫性，exceptset用于檢查異常數據，具體用法如下：
假定我們想測試一個套接字是否可讀，必須將該套接字增加到readset中，再等待select函數完成，完成后判斷該套接字是否仍然是readset集合的一部分，是，則該套接字可讀。三個參數至少有一個不為null。
其中的timeval的結構如下：
struct timeval
{
long tv_sec; (秒)
long tv_usec; (毫秒)
}
如select函數調用失敗，返回SOCKET_ERROR.
對fd_set集合進行操作，可用宏：
FD_CLR(s,*set)：從set中刪除套接字s；
FD_ISSET(s,*set):檢查s是否是set集合的一員，返回true或false
FD_SET(s,*set):將套接字s加入集合set
FD_ZERO(*set)：將set初始化為空集合。
WSAAsyncSelect 模型
利用這個模型，應用程序可在一個套接字上接收以Windows消息為基礎的網絡時間通知。使用這種模型，必須提供一個“窗口”，用于接收消息。函數原型如下：
int WSAAsyncSelect(
SOCKET s,
HWND hwnd,
unsigned int wMsg,
Long lEvent
);
s:對應套接字
hwnd：接收消息的窗體句柄
wMsg：發送的消息，應該為一個比WM_USER大的值。
IEvent：對應為一系列網絡事件的組合，包括：FD_READ,FD_WRITE,FD_ACCEPT,FD_CONNECT,FD_CLOSE.
如：WSAAsyncSelect（s,hwnd,WM_SOCKET,FD_CONNECT|FD_READ|FD_WRITE|FD_CLOSE）
在調用WSAAsyncSelect后，即在hwnd對應的窗體回調函數中對網絡事件（消息）進行處理：
LRESULT CALLBACK WindowProc(
HWND hWnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam
);
其中wParam指定在其上面發生了一個網絡事件的套接字。
lParam低字節指定了已經發生的網絡事件，而lParam的高字節包含了可能出現的錯誤代碼。在網絡事件消息到達的時候，先調用WSAGETSELECTERROR宏返回高字節包含的錯誤信息。若沒有錯誤，則調用WSAGETSELECTEVENT宏返回lParam低字節部分。
WSAEventSelect 模型
和WSAAsyncSelect模型不同的是，這種模型中網絡事件會投遞至一個事件對象句柄，而非窗口句柄。所以要求我們針對每一個套接字都要建立一個事件對象。用WSACreateEvent函數，定義如下：
WSAEVENT WSACreateEvent(void);
然后調用WSAEventSelect函數，定義如下：
int WSAEventSelect(
SOCKET s;
WSAEVENT hEventObject,
long lNetworkEvents
);
鑒于這個模型的復雜性，還是用代碼說話吧：
#include
#include
#include
#define PORT 5150
#define DATA_BUFSIZE 8192
typedef struct _SOCKET_INFORMATION {
CHAR Buffer[DATA_BUFSIZE];
WSABUF DataBuf;
SOCKET Socket;
DWORD BytesSEND;
DWORD BytesRECV;
} SOCKET_INFORMATION, * LPSOCKET_INFORMATION;
BOOL CreateSocketInformation(SOCKET s);
void FreeSocketInformation(DWORD Event);
DWORD EventTotal = 0;
WSAEVENT EventArray[WSA_MAXIMUM_WAIT_EVENTS];
LPSOCKET_INFORMATION SocketArray[WSA_MAXIMUM_WAIT_EVENTS];
void main(void)
{
SOCKET Listen;
SOCKET Accept;
SOCKADDR_IN InternetAddr;
DWORD Event;
WSANETWORKEVENTS NetworkEvents;
WSADATA wsaData;
DWORD Ret;
DWORD Flags;
DWORD RecvBytes;
DWORD SendBytes;
if ((Ret = WSAStartup(0x0202, &wsaData)) != 0) //初始化winsock
{
printf("WSAStartup() failed with error %d\n", Ret);
return;
}
if ((Listen = socket (AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) //創建Listen套接字
{
printf("socket() failed with error %d\n", WSAGetLastError());
return;
}
CreateSocketInformation(Listen); //創建一個_SOCKET_INFORMATION結構實體
if (WSAEventSelect(Listen, EventArray[EventTotal - 1], FD_ACCEPT|FD_CLOSE) == SOCKET_ERROR)
{
printf("WSAEventSelect() failed with error %d\n", WSAGetLastError());
return;
}
InternetAddr.sin_family = AF_INET;
InternetAddr.sin_addr.s_addr = htonl(INADDR_ANY);
InternetAddr.sin_port = htons(PORT);
if (bind(Listen, (PSOCKADDR) &InternetAddr, sizeof(InternetAddr)) == SOCKET_ERROR)
{
printf("bind() failed with error %d\n", WSAGetLastError());
return;
}
if (listen(Listen, 5))
{
printf("listen() failed with error %d\n", WSAGetLastError());
return;
}
while(TRUE)
{
// Wait for one of the sockets to receive I/O notification and
if ((Event = WSAWaitForMultipleEvents(EventTotal, EventArray, FALSE,
WSA_INFINITE, FALSE)) == WSA_WAIT_FAILED)
{
printf("WSAWaitForMultipleEvents failed with error %d\n", WSAGetLastError());
return;
}
//通過SocketArray[Event - WSA_WAIT_EVENT_0]獲得事件是在哪個socket上發生
//通過WSAEnumNetworkEvents獲得發生了什么類型的網絡事件
if (WSAEnumNetworkEvents(SocketArray[Event - WSA_WAIT_EVENT_0]->Socket, EventArray[Event -
WSA_WAIT_EVENT_0], &NetworkEvents) == SOCKET_ERROR) //必須減去預定義值，才能得到實際的索引位置
{
printf("WSAEnumNetworkEvents failed with error %d\n", WSAGetLastError());
return;
}
if (NetworkEvents.lNetworkEvents & FD_ACCEPT)
{
if (NetworkEvents.iErrorCode[FD_ACCEPT_BIT] != 0)
{
printf("FD_ACCEPT failed with error %d\n", NetworkEvents.iErrorCode[FD_ACCEPT_BIT]);
break;
}
if ((Accept = accept(SocketArray[Event - WSA_WAIT_EVENT_0]->Socket, NULL, NULL)) == INVALID_SOCKET)
{
printf("accept() failed with error %d\n", WSAGetLastError());
break;
}
if (EventTotal > WSA_MAXIMUM_WAIT_EVENTS)
{
printf("Too many connections - closing socket.\n");
closesocket(Accept);
break;
}
CreateSocketInformation(Accept);//一旦有套接字accepted了，就創建事件對象和LPSOCKET_INFORMATION 結構
if (WSAEventSelect(Accept, EventArray[EventTotal - 1], FD_READ|FD_WRITE|FD_CLOSE) == SOCKET_ERROR) //繼續對accepted 的 套接字調用WSAEventSelect
{
printf("WSAEventSelect() failed with error %d\n", WSAGetLastError());
return;
}
printf("Socket %d connected\n", Accept);
}
// Try to read and write data to and from the data buffer if read and write events occur.
if (NetworkEvents.lNetworkEvents & FD_READ ||
NetworkEvents.lNetworkEvents & FD_WRITE)
{
if (NetworkEvents.lNetworkEvents & FD_READ &&
NetworkEvents.iErrorCode[FD_READ_BIT] != 0)
{
printf("FD_READ failed with error %d\n", NetworkEvents.iErrorCode[FD_READ_BIT]);
break;
}
if (NetworkEvents.lNetworkEvents & FD_WRITE &&
NetworkEvents.iErrorCode[FD_WRITE_BIT] != 0)
{
printf("FD_WRITE failed with error %d\n", NetworkEvents.iErrorCode[FD_WRITE_BIT]);
break;
}
LPSOCKET_INFORMATION SocketInfo = SocketArray[Event - WSA_WAIT_EVENT_0];
// Read data only if the receive buffer is empty.
if (SocketInfo->BytesRECV == 0)
{
SocketInfo->DataBuf.buf = SocketInfo->Buffer;
SocketInfo->DataBuf.len = DATA_BUFSIZE;
Flags = 0;
if (WSARecv(SocketInfo->Socket, &(SocketInfo->DataBuf), 1, &RecvBytes,
&Flags, NULL, NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != WSAEWOULDBLOCK)
{
printf("WSARecv() failed with error %d\n", WSAGetLastError());
FreeSocketInformation(Event - WSA_WAIT_EVENT_0);
return;
}
}
else
{
SocketInfo->BytesRECV = RecvBytes;
}
}
// Write buffer data if it is available.
if (SocketInfo->BytesRECV > SocketInfo->BytesSEND)
{
SocketInfo->DataBuf.buf = SocketInfo->Buffer + SocketInfo->BytesSEND;
SocketInfo->DataBuf.len = SocketInfo->BytesRECV - SocketInfo->BytesSEND;
if (WSASend(SocketInfo->Socket, &(SocketInfo->DataBuf), 1, &SendBytes, 0,
NULL, NULL) == SOCKET_ERROR)
{
if (WSAGetLastError() != WSAEWOULDBLOCK)
{
printf("WSASend() failed with error %d\n", WSAGetLastError());
FreeSocketInformation(Event - WSA_WAIT_EVENT_0);
return;
}
// A WSAEWOULDBLOCK error has occured. An FD_WRITE event will be posted
// when more buffer space becomes available
}
else
{
SocketInfo->BytesSEND += SendBytes;
if (SocketInfo->BytesSEND == SocketInfo->BytesRECV)
{
SocketInfo->BytesSEND = 0;
SocketInfo->BytesRECV = 0;
}
}
}
}
if (NetworkEvents.lNetworkEvents & FD_CLOSE)
{
if (NetworkEvents.iErrorCode[FD_CLOSE_BIT] != 0)
{
printf("FD_CLOSE failed with error %d\n", NetworkEvents.iErrorCode[FD_CLOSE_BIT]);
break;
}
printf("Closing socket information %d\n", SocketArray[Event - WSA_WAIT_EVENT_0]->Socket);
FreeSocketInformation(Event - WSA_WAIT_EVENT_0);
}
}
return;
}
BOOL CreateSocketInformation(SOCKET s)
{
LPSOCKET_INFORMATION SI;
if ((EventArray[EventTotal] = WSACreateEvent()) == WSA_INVALID_EVENT)
{
printf("WSACreateEvent() failed with error %d\n", WSAGetLastError());
return FALSE;
}
if ((SI = (LPSOCKET_INFORMATION) GlobalAlloc(GPTR,
sizeof(SOCKET_INFORMATION))) == NULL)
{
printf("GlobalAlloc() failed with error %d\n", GetLastError());
return FALSE;
}
// Prepare SocketInfo structure for use.
SI->Socket = s;
SI->BytesSEND = 0;
SI->BytesRECV = 0;
SocketArray[EventTotal] = SI;
EventTotal++;
return(TRUE);
}
void FreeSocketInformation(DWORD Event)
{
LPSOCKET_INFORMATION SI = SocketArray[Event];
DWORD i;
closesocket(SI->Socket);
GlobalFree(SI);
WSACloseEvent(EventArray[Event]);
// Squash the socket and event arrays
for (i = Event; i < EventTotal; i++)
{
EventArray[i] = EventArray[i + 1];
SocketArray[i] = SocketArray[i + 1];
}
EventTotal--;
}
有了源代碼，一切都是那么清晰，呵呵。
終于可以進入重疊模型了。。。
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