WinSock2 c++ what happens when accept(...) method is called - c++

Question

I am following the Getting Started with WinSock guide (here) from Microsoft.
In my situation I have a java application that act as the client, and a c++ application for the server.
Here is the server code so far:
//all includes
int main()
{
WSADATA wsaData;
int iResult;
SOCKET listenSocket = INVALID_SOCKET;
SOCKET clientSocket = INVALID_SOCKET;
struct addrinfo *result = NULL;
struct addrinfo hints;
int iSendResult;
char recvbuf[DEFAULT_BUFLEN];
int recvbuflen = DEFAULT_BUFLEN;
//Initialization
iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
else {
printf("WSAStartup success !\n");
}
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
//Resolve the server adress and port
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if (iResult != 0) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
listenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (listenSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
//Setup the TCP listening socket
iResult = bind(listenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(listenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
iResult = listen(listenSocket, SOMAXCONN);
if (iResult == SOCKET_ERROR) {
printf("listen failed with error: %d\n", WSAGetLastError());
closesocket(listenSocket);
WSACleanup();
return 1;
}
clientSocket = accept(listenSocket, NULL, NULL);
if (clientSocket == INVALID_SOCKET) {
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(listenSocket);
WSACleanup();
return 1;
}
//No longer need server socket
closesocket(listenSocket);
// Receive until the peer shuts down the connection
do {
iResult = recv(clientSocket, recvbuf, recvbuflen, 0);
printf("result : %d", iResult);
//Receive data
if (iResult > 0) {
printf("Bytes received: %d\n", iResult);
printf("Message: %s\n Sending response to client... ", recvbuf);
const char* response = "Hello from key/mouse emulator app server";
iSendResult = send(clientSocket, response, sizeof(char) * (strlen(response)+1), 0);
if (iSendResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(clientSocket);
WSACleanup();
return 1;
}
printf("Bytes sent: %d\n", iSendResult);
}
else if (iResult == 0)
printf("Connection closing...\n");
else {
printf("recv failed with error: %d\n", WSAGetLastError());
closesocket(clientSocket);
WSACleanup();
return 1;
}
} while (iResult > 0);
// shutdown the connection since we're done
iResult = shutdown(clientSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(clientSocket);
WSACleanup();
return 1;
}
// cleanup
closesocket(clientSocket);
WSACleanup();
system("PAUSE");
return 0;
}
My understanding was that in the do...while loop it was listening to any incoming data from the client. So I tried to debug to check what kind of values I have in iResult when nothing is sent.
I found out using Visual Studio community 2017 that I could not go further this line :
clientSocket = accept(listenSocket, NULL, NULL);
And it would only go in the do...while when the client sent some data.
So my question is what happens in the program when I reach accept(...) line?