C++ Socket application closes for no reason - c++

Question

Basically I am creating a socket server in C++ which accepts connections, and then creates threads to send data to those connections.
For this I've used a while loop which basically is:
while (TRUE){
listen_sock = listen(sock, SOMAXCONN);
if (listen_sock == 0){
accept_sock = accept(sock, NULL, NULL);
if(accept_sock == INVALID_SOCKET){
cout << "part 5\n";
printf("accepting connection failed with error: %d\n", WSAGetLastError());
}
thread thrd(send_dat, accept_sock);
thrd.detach();
}
else if (listen_sock == SOCKET_ERROR){
cout << "part 4\n";
printf("\n\nlistening on socket failed with error: %d\n", WSAGetLastError());
}
}
Basically send_dat(SOCKET accept_sock) is a function that just sends data to accept_sock socket:
void send_dat(SOCKET accept_sock){
/*variable declarations here*/
data = recv(accept_sock, recvbuf, recvbuflen, 0);
if (data == SOCKET_ERROR){
cout << "part -1\n";
throw runtime_error("Failed to receive data");
WSAGetLastError();
}
data_res = response(data);
send_sock = send(accept_sock, data_res_len, data_res, 0);
if (send_sock == SOCKET_ERROR){
cout << "part -2\n";
throw runtime_error("Failed to send data");
WSAGetLastError();
}
}
The problem is that whenever I run it, it just closes after sending data to one user once, without any error or messages.
Why is this happening? Please help.