如何在C语言中判断socket是否已经断开

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bool IsSocketClosed(SOCKET clientSocket) 
{ 
 bool ret = false; 
 HANDLE closeEvent = WSACreateEvent(); 
 WSAEventSelect(clientSocket, closeEvent, FD_CLOSE); 
 
 DWORD dwRet = WaitForSingleObject(closeEvent, 0); 
 
 if(dwRet == WSA_WAIT_EVENT_0) 
 ret = true; 
 else if(dwRet == WSA_WAIT_TIMEOUT) 
 ret = false; 
 
 WSACloseEvent(closeEvent); 
 return ret; 
} 
 

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#include <errno.h> 
 
bool IsSocketClosed(int clientSocket) 
{ 
 char buff[32]; 
 int recvBytes = recv(clientSocket, buff, sizeof(buff), MSG_PEEK); 
 
 int sockErr = errno; 
 
 //cout << "In close function, recv " << recvBytes << " bytes, err " << sockErr << endl; 
 
 if( recvBytes > 0) //Get data 
 return false; 
 
 if( (recvBytes == -1) && (sockErr == EWOULDBLOCK) ) //No receive data 
 return false; 
 
 return true; 
}