过滤来自特定IP的UDP数据包

void *receive_thread_body(void *arg)
{
  long msg = 0;

  while(msg<500)
  {
    fd_set socket_set;
    FD_ZERO(&socket_set);
    FD_SET(b_sock,&socket_set);
    struct timeval tm;
    tm.tv_usec = 10;
    tm.tv_sec = 0;

    int ret = select(b_sock+1,&socket_set,0,0,&tm);

    if(ret == -1)
    {
      std::cout<<\"select failed\";
    }

    if(FD_ISSET(b_sock,&socket_set) != 0)
    {
      int recvStringLen = recvfrom(b_sock, &msg, sizeof(msg), 0, NULL, 0);
      if(recvStringLen < 0)
      {
        std::cout<<\"recvfrom failed\";
      }
      else
      {
        printf(\"\\t\\t\\tRX: %d\\n\",msg);
      }
    }
  }
}