How is send data without lwip func.

Hi;
i use lwip tcp/ip raw..
tcp_echoserver.c is running my project.It's working no problem.
But i want send data while loop in main.c..
i write;

while(1)
{ mx_lwip_process(); hal_delay(250); tcp_write(pcb,"lalala",6,1);
}

this code with is not receive data from pc(telnet)

static err_t tcp_server_poll(void *arg, struct tcp_pcb *pcb)
{ tcp_write(pcb,"lalala",6,1);
}

this code is working, i receive data from pc(telnet)

How is send data without lwip func. ?

Regards...