reading and writing simultaneously from the same socket in windows - c++

Question

I'm writing a server in C++ on windows. On connection, the server creates two threads to handle the request - one constantly reading the input from the socket and the second constantly writes output to it. I'm experiencing problems with it because when there's no input from the client but output to send to it thread #1 is blocking on recv() making thread two block on send() and not write it's data.
Is there a way to send() to a socket although it is already in blocking recv()?
Thanks
EDIT:
I took out the relevant code and reproduced the issue. if I comment out the AfxThreadCall to the readThread, the data is being sent. otherwise it isn't. the client is a simple client that prints what it recieves.
SOCKET m_sockIOSrv = NULL;
SOCKET m_sockIO = NULL;
UINT readThread(LPVOID args)
{
WSABUF DataBuf;
DWORD RecvBytes;
DWORD Flags = 0 ;
char buf[4096];
DataBuf.len = 4096;
DataBuf.buf = buf;
while (true)
{
int ret = WSARecv(m_sockIO, &DataBuf, 1, &RecvBytes, &Flags, NULL, NULL); // Read some data...
if (ret == SOCKET_ERROR)
{
printf("ERROR: WSARecv: %d", WSAGetLastError());
return 1;
}
printf("jobleader - got %d from recv\n", RecvBytes);
}
return 0;
}
UINT writeThread(LPVOID args)
{
WSABUF DataBuf;
DWORD SendBytes;
DWORD Flags;
char buf[] = { 'a', 'a', 'a' };
DataBuf.len = 3;
DataBuf.buf = buf;
while (true)
{
DWORD dwWritten;
WSASend(m_sockIO, &DataBuf, 1, &dwWritten, 0, NULL, NULL);
}
return 0;
}
SOCKET ServerSocket(unsigned int & port) {
// Our server socket
SOCKET s = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, 0);
if (s == INVALID_SOCKET)
return s;
SOCKADDR sa;
sa.sa_family = AF_INET;
memset(sa.sa_data, 0, sizeof(sa.sa_data));
if (bind(s, &sa, sizeof(sa))) {
closesocket(s);
return INVALID_SOCKET;
}
struct sockaddr_in sa_in;
int sz = sizeof(sa_in);
if (getsockname(s, (struct sockaddr *)&sa_in, &sz)) {
closesocket(s);
return INVALID_SOCKET;
}
if (listen(s, 50)) {
closesocket(s);
return INVALID_SOCKET;
}
port = ntohs(sa_in.sin_port);
return s;
}
int _tmain(int argc, _TCHAR* argv[])
{
unsigned int ioPort = 0;
WORD wVersionRequested = MAKEWORD(2, 2);
WSADATA wsaData;
if (WSAStartup(wVersionRequested, &wsaData))
{
if (!AfxSocketInit())
{
printf("ERROR: Unable to initialize WinSock DLL");
exit(2);
}
}
m_sockIOSrv = ServerSocket(ioPort);
if (m_sockIOSrv == INVALID_SOCKET) {
int lastError = GetLastError();
printf("ERROR: StartIOSockets Failed to start socket %d.\n",lastError);
return 1;
}
printf("Listening on %d\n", ioPort);
m_sockIO = accept(m_sockIOSrv, NULL, NULL);
AfxBeginThread(&readThread, (LPVOID)NULL);
AfxBeginThread(&writeThread, (LPVOID)NULL);
getchar();
}