why my TCP server code send a SYN/ACK on only first packet or only on the first connection?

SOCKET sock;
SOCKET fd;
uint16 port = 18001;

void CreateSocket()
{
   struct sockaddr_in server, client;  // creating a socket address structure: structure contains ip address and port number
  WORD wVersionRequested;
WSADATA wsaData;
int len;

    printf("Initializing Winsock\n");


    wVersionRequested = MAKEWORD (2, 2);
    iResult =  WSAStartup (wVersionRequested, &wsaData);      
if (iResult != NO_ERROR)
  printf("Error at WSAStartup()\n"); 


    // create socket
    sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock < 0)    {
        printf("Could not Create Socket\n");
        //return 0;
    }

    printf("Socket Created\n");




    // create socket address of the server
    memset( &server, 0, sizeof(server));
    // IPv4 - connection
    server.sin_family = AF_INET;
    // accept connections from any ip adress
    server.sin_addr.s_addr = htonl(INADDR_ANY);
    // set port
    server.sin_port = htons(18001);


    //Binding between the socket and ip address
    if(bind (sock, (struct sockaddr *) &server, sizeof(server)) < 0)
    {
        printf("Bind failed with error code: %d", WSAGetLastError());
    }

    //Listen to incoming connections
    if(listen(sock,3) == -1){
        printf("Listen failed with error code: %d", WSAGetLastError());
    }

    printf("Server has been successfully set up - Waiting for incoming connections");

    for(;;){
        len = sizeof(client);
        fd = accept(sock, (struct sockaddr*) &client, &len);

        if (fd < 0){
            printf("Accept failed");
            close(sock);
        }
        //echo(fd);
        printf("\n Process incoming connection from (%s , %d)", inet_ntoa(client.sin_addr),ntohs(client.sin_port));
//closesocket(fd);
    }

}

The server code is accepting a connection from the client via the ip address and the port number. It is sending SYN/ACK to the client only during the first connection and It is sending like below for the second time: RST / ACK (it is resetting during the second time).

Could anyone tell me what is the error in the above code ??