for循环计数问题，为什么下列程序返回NULL需要30s

while(1)
    {
        int i;
        for(i=0;i<2;i++){}
        ret = Serial_Recv(serialfd, readbuf,sizeof(readbuf));  
        if(ret > 0)  
        {  
            readbuf[ret] = '\0';  
            if(!(ret=strcmp(readbuf,"ok")))
            {
                result="Available";
                memset(readbuf,0,sizeof(readbuf));
                Serial_Send(serialfd, sendbuf, strlen(sendbuf)+1); 
                if(serialfd>0)
                    {
                        close(serialfd);
                    }
                break;   
            }           
            else  
            {  
                result="Unknown command"; 
                break;
            }                            
        }
        else if(i==2)
        {
            result="NULL";
            break;
        }    
        sleep(2);
    }

}