I have just compiled this code: http://www.win32developer.com/tutorial/winsock/winsock_tutorial_2.shtm
I have added some codes so it does recv(), in an infinite loop. My problem, if there is no data to read, it still does not block.
Am I totally mistaken if I think recv should block in my case?
The code I have added is:
for(;;)
{
char buffer[1000];
memset(buffer,0,999);
int inDataLength = recv(Socket,buffer,1000,0);
int nError=WSAGetLastError();
if(nError!=WSAEWOULDBLOCK&&nError!=0)
{
std::cout<<"Winsock error code: "<<nError<<"\r\n";
std::cout<<"Client disconnected!\r\n";
// Shutdown our socket
shutdown(Socket,SD_SEND);
// Close our socket entirely
closesocket(Socket);
break;
}
}
It is at the end, after the std::cout<<"Client connected!\\r\\n\\r\\n";
line. I know I copied this from a "non blocking" example, but I dont think this code should do anything nonblocking really, still, my for loop is running like mad!
recv
should block by default, unless there's a socket error or you explicitly set the socket to non-blocking. Be sure to check the return value for error. For more information see the Microsofts MSDN article on recv .
The loop is not checking for errors correctly. It needs to be more like this instead:
char buffer[1000];
int inDataLength;
do
{
inDataLength = recv(Socket, buffer, sizeof(buffer), 0);
if (inDataLength > 0)
{
// inDataLength number of bytes were received, use buffer as needed...
continue;
}
if (inDataLength == 0)
{
std::cout << "Client disconnected!" << std::endl;
break;
}
int nError = WSAGetLastError();
if (nError != WSAEWOULDBLOCK)
{
std::cout << "Winsock error code: " << nError << std::endl;
break;
}
// optionally call select() here to wait for the socket
// to receive data before calling recv() again...
/*
fd_set fd;
FD_ZERO(&fd);
FD_SET(Socket, &fd);
timeval tv;
tv.tv_sec = ...;
tv.tv_usec = ...;
nError = select(Socket+1, &fd, NULL, NULL, &tv);
if (nError == 0)
{
std::cout << "Timeout waiting for data" << std::endl;
break;
}
if (nError == SOCKET_ERROR)
{
nError = WSAGetLastError();
std::cout << "Winsock error code: " << nError << std::endl;
break;
}
*/
}
while (true);
// Shutdown our socket
shutdown(Socket, SD_SEND);
// Close our socket entirely
closesocket(Socket);
if((nError == SOCKET_ERROR) || (nError == 0))
WSAGetLastError();
else
; // handle success
That's how it should look, and not how you did it.
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