how to make a blocking recv call - c++

Question

it may be a strange request, but, actually, I would like make my call to recv() blocking.
It appears that it should be blocking by default, but for me, it is not, and I can't find any way to make it.
I have a very simple server application, "open socket - bind - wait for connection - receive" on one hand,
and, on the other hand, a simple "open socket - connect - send" client application.
They communicate on LocalHost.
Server :
int clTcpServer::openSocket(void)
{
this->__iLocalSocketId = socket(AF_INET, //stand for IPV4
SOCK_STREAM, //using TCP protocol
0); //no specified / ip protocol
return 0;
}
int clTcpServer::openServer(uint16_t u16Port)
{
this->__strServerInfo.sin_family = AF_INET; // stand for IPV4
this->__strServerInfo.sin_addr.s_addr = INADDR_ANY; // Listen to any address (no filter)
this->__strServerInfo.sin_port = htons(u16Port);
if(bind(this->__iLocalSocketId, (sockaddr *)&this->__strServerInfo, sizeof(this->__strServerInfo)) < 0)
{
std::cout << "TCP server - ERROR - Can't bind socket to port " << std::dec << (int)u16Port << std::endl;
return -1;
}
std::cout << "TCP server - Server opened" << std::endl;
listen(this->__iLocalSocketId, 3);
return 0;
}
int clTcpServer::waitForConnection(void)
{
int iClientIpInfo;
char* pcClientIp;
std::cout << "Waiting for connection ..." << std::endl;
iClientIpInfo = sizeof(struct sockaddr_in);
this->__iDistantSocketId = accept(this->__iLocalSocketId,
(sockaddr *)&this->__strClientInfo,
(socklen_t*)&iClientIpInfo);
if(this->__iDistantSocketId < 0)
{
std::cout << "TCP server - ERROR - Connection refused" << std::endl;
return -1;
}
pcClientIp = inet_ntoa(this->__strClientInfo.sin_addr);
std::cout << "Connection accepted from " << pcClientIp << std::endl;
return 0;
}
int clTcpServer::receiveDataBuffer(void * pvidBuffer, size_t sizeMaxBufferSize)
{
int iRecvSize;
iRecvSize = recv(this->__iDistantSocketId, pvidBuffer, sizeMaxBufferSize, (int)0);
if (iRecvSize < (int)0 )
{
std::cout << "TCP server - ERROR - Recv failed" << std::endl;
return -1;
}
return iSentSize;
}
Client :
int clTcpClient::openSocket(void)
{
/* Create a new socket for client comm. */
this->__iSocketId = socket( AF_INET, //stand for IPV4
SOCK_STREAM, //using TCP protocol
0); //no specified / ip protocol
if (this->__iSocketId == (int)-1)
{
std::cout << "TCP client - ERROR - Can't open Socket" << std::endl;
return -1;
}
return 0;
}
int clTcpClient::connectToServer(std::string stgIpAddress, uint16_t u16Port)
{
/* configure server info according to parameters */
this->__strServerInfo.sin_family = AF_INET; //stand for IPV4
this->__strServerInfo.sin_port = htons(u16Port);
/* Retrieve IP addr*/
this->__strServerInfo.sin_addr.s_addr = inet_addr(stgIpAddress.c_str());
/* Try to connect to the server */
if (connect(this->__iSocketId,
(sockaddr*)&this->__strServerInfo,
sizeof(this->__strServerInfo)) < 0)
{
std::cout << "TCP client - ERROR - Can't connect to " << stgIpAddress << ":" << std::dec << (int)u16Port << std::endl;
return -1;
}
std::cout << "TCP client - Connected" << std::endl;
return 0;
}
int clTcpClient::sendDataBuffer(const void *kpvidData, size_t sizeDataLength)
{
ssize_t sizeSentSize;
/* Send the buffer */
sizeSentSize = send(this->__iSocketId, kpvidData, sizeDataLength, (int)0);
if (sizeSentSize < (ssize_t)0 )
{
std::cout << "TCP client - ERROR - Send failed" << std::endl;
return -1;
}
std::cout << "TCP client - " << (int)sizeSentSize << " byte(s) sent." << std::endl;
return 0;
}
This is working fine, but recv() here is not blocking. If I call it (after having initialized all the stuff, of course), if there is nothing to receive, the function returns 0, as "0 byte received", and that's all.
It means If I want to put this recv function in a loop, CPU is working 100% to receive ... nothing.
What's wrong here ?How can I make it blocking ?
Thank you