select()实现

#include <winsock2.h>#include <windows.h>#include <stdio.h>#define PORT 5150#define DATA_BUFSIZE 8192typedef struct _SOCKET_INFORMATION {   CHAR Buffer[DATA_BUFSIZE];   WSABUF DataBuf;   SOCKET Socket;   OVERLAPPED Overlapped;   DWORD BytesSEND;   DWORD BytesRECV;} SOCKET_INFORMATION, * LPSOCKET_INFORMATION;BOOL CreateSocketInformation(SOCKET s);void FreeSocketInformation(DWORD Index);DWORD TotalSockets = 0;LPSOCKET_INFORMATION SocketArray[FD_SETSIZE];void main(void){   SOCKET ListenSocket;   SOCKET AcceptSocket;   SOCKADDR_IN InternetAddr;   WSADATA wsaData;   INT Ret;   FD_SET WriteSet;   FD_SET ReadSet;   DWORD i;   DWORD Total;   ULONG NonBlock;   DWORD Flags;   DWORD SendBytes;   DWORD RecvBytes;   if ((Ret = WSAStartup(0x0202,&wsaData)) != 0)   {      printf("WSAStartup() failed with error %d\n", Ret);      WSACleanup();      return;   }   // Prepare a socket to listen for connections.   if ((ListenSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0,      WSA_FLAG_OVERLAPPED)) == INVALID_SOCKET)    {      printf("WSASocket() 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(ListenSocket, (PSOCKADDR) &InternetAddr, sizeof(InternetAddr))      == SOCKET_ERROR)   {      printf("bind() failed with error %d\n", WSAGetLastError());      return;   }   if (listen(ListenSocket, 5))   {      printf("listen() failed with error %d\n", WSAGetLastError());      return;   }   // Change the socket mode on the listening socket from blocking to   // non-block so the application will not block waiting for requests.   NonBlock = 1;   if (ioctlsocket(ListenSocket, FIONBIO, &NonBlock) == SOCKET_ERROR)   {      printf("ioctlsocket() failed with error %d\n", WSAGetLastError());      return;   }   while(TRUE)   {      // Prepare the Read and Write socket sets for network I/O notification.      FD_ZERO(&ReadSet);      FD_ZERO(&WriteSet);      // Always look for connection attempts.      FD_SET(ListenSocket, &ReadSet);      // Set Read and Write notification for each socket based on the      // current state the buffer.  If there is data remaining in the      // buffer then set the Write set otherwise the Read set.      for (i = 0; i < TotalSockets; i++)         if (SocketArray[i]->BytesRECV > SocketArray[i]->BytesSEND)            FD_SET(SocketArray[i]->Socket, &WriteSet);         else            FD_SET(SocketArray[i]->Socket, &ReadSet);      if ((Total = select(0, &ReadSet, &WriteSet, NULL, NULL)) == SOCKET_ERROR)      {         printf("select() returned with error %d\n", WSAGetLastError());         return;      }      // Check for arriving connections on the listening socket.      if (FD_ISSET(ListenSocket, &ReadSet))      {         Total--;         if ((AcceptSocket = accept(ListenSocket, NULL, NULL)) != INVALID_SOCKET)         {            // Set the accepted socket to non-blocking mode so the server will            // not get caught in a blocked condition on WSASends            NonBlock = 1;            if (ioctlsocket(AcceptSocket, FIONBIO, &NonBlock) == SOCKET_ERROR)            {               printf("ioctlsocket() failed with error %d\n", WSAGetLastError());               return;            }            if (CreateSocketInformation(AcceptSocket) == FALSE)               return;         }         else         {            if (WSAGetLastError() != WSAEWOULDBLOCK)            {               printf("accept() failed with error %d\n", WSAGetLastError());               return;            }         }      }      // Check each socket for Read and Write notification until the number      // of sockets in Total is satisfied.      for (i = 0; Total > 0 && i < TotalSockets; i++)      {         LPSOCKET_INFORMATION SocketInfo = SocketArray[i];         // If the ReadSet is marked for this socket then this means data         // is available to be read on the socket.         if (FD_ISSET(SocketInfo->Socket, &ReadSet))         {            Total--;            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(i);               }               continue;            }             else            {               SocketInfo->BytesRECV = RecvBytes;               // If zero bytes are received, this indicates the peer closed the               // connection.               if (RecvBytes == 0)               {                  FreeSocketInformation(i);                  continue;               }            }         }         // If the WriteSet is marked on this socket then this means the internal         // data buffers are available for more data.         if (FD_ISSET(SocketInfo->Socket, &WriteSet))         {            Total--;            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(i);               }               continue;            }            else            {               SocketInfo->BytesSEND += SendBytes;               if (SocketInfo->BytesSEND == SocketInfo->BytesRECV)               {                  SocketInfo->BytesSEND = 0;                  SocketInfo->BytesRECV = 0;               }            }         }      }   }}BOOL CreateSocketInformation(SOCKET s){   LPSOCKET_INFORMATION SI;         printf("Accepted socket number %d\n", s);   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[TotalSockets] = SI;   TotalSockets++;   return(TRUE);}void FreeSocketInformation(DWORD Index){   LPSOCKET_INFORMATION SI = SocketArray[Index];   DWORD i;   closesocket(SI->Socket);   printf("Closing socket number %d\n", SI->Socket);   GlobalFree(SI);   // Squash the socket array   for (i = Index; i < TotalSockets; i++)   {      SocketArray[i] = SocketArray[i + 1];   }   TotalSockets--;}