Подключение библиотеки

#include <stdio.h>
#include <winsock2.h>
#include <windows.h>
 
#define MY_PORT 666
 
#define PRINTNUSERS if(nclients) printf("%d user on-line \n", nclients); else printf("No users online\n");
 
DWORD WINAPI SexToClient(LPVOID client_socket);
 
int nclients = 0;
 
int main(int argc, char *argv[])
{
  char buff[1024];
  
  printf("TCP SERVER DEMO\n");
  
  if(WSAStartup(0x0202, (WSADATA*)&buff[0]))
  {
    printf("Error socket %d\n", WSAGetLastError());
    WSACleanup();
    return -1;
  } 
  
  SOCKET mysocket;
  
  if((mysocket = socket(AF_INET,SOCK_STREAM,0)) < 0)
  {
    printf("Error socket %d\n", WSAGetLastError());
    WSACleanup();
    return -1;
  }
  
  sockaddr_in local_addr;
  local_addr.sin_family = AF_INET;
  local_addr.sin_port = htons(MY_PORT);
  local_addr.sin_addr.s_addr = 0;
  
  if(bind(mysocket, (sockaddr *)&local_addr, sizeof(local_addr)))
  {
    printf("Error bind %d\n", WSAGetLastError());
    closesocket(mysocket);
    WSACleanup();
    return -1;
  }
  
  if(listen(mysocket, 0x100))
  {
    printf("Error listen %d\n", WSAGetLastError);
    closesocket(mysocket);
    WSACleanup();
    return -1;
  }
  
  printf("Ojidanie podklucheniy\n");
  
  SOCKET client_socket;
  sockaddr_in client_addr;
  
  int client_addr_size = sizeof(client_addr);
  
  while(client_socket = accept(mysocket, (sockaddr *)&client_addr, &client_addr_size));
  {
    HOSTENT *hst;
    hst = gethostbyaddr((char *) &client_addr.sin_addr.s_addr, 4, AF_INET);
    
    printf("+%s [%s] new connect!\n",
    (hst)?hst->h_name:"", inet_ntoa(client_addr.sin_addr));
    PRINTNUSERS
  
    DWORD thID;
    CreateThread(NULL, NULL, SexToClient, &client_socket, NULL, &thID);
  }
  return 0;
}
 
DWORD WINAPI SexToClient(LPVOID client_socket)
{
  SOCKET my_sock;
  my_sock = ((SOCKET *) client_socket)[0];  
  char buff [20 * 1024];
  #define sHELLO "Hello, Sailor\r\n"
  
  send(my_sock, sHELLO, sizeof(sHELLO), 0);
  
  int bytes_recv = 0;
   while( (bytes_recv=recv(my_sock,&buff[0],sizeof(buff),0))&& bytes_recv !=SOCKET_ERROR)
      send(my_sock,&buff[0],bytes_recv,0);   
  
  nclients--;
  
  printf("-disconect\n"); PRINTNUSERS
  
  closesocket(my_sock);
  return 0;      
}