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how to extract data from ethernet at the reception

Question asked by TARHAN SAMAH on Mar 28, 2018
Latest reply on Apr 5, 2018 by TARHAN SAMAH

Hello im using stm32f429ZI NUCLEO (with server application netconn) , protocol tcp for sending and receiving data using ethernet ,, i can send no prblm , i receive also but i need to save like a serie , i use this server example this way:



void StartDefaultTask(void const * argument)
//struct netconn *conn, *newconn;
err_t err, accept_err;
struct netbuf *buf;
void *data;
//char *data=pvPortMalloc(2048);---------->here i confuse which is the right definition of data??????

//char data[100];
err_t recv_err;
uint16_t len=0;
ip_addr_t local_ip;//stm32
ip_addr_t remote_ip;//pc host
uint8_t i=0;

/* init code for LWIP */

printf("ETHERNET STM32F429ZI lwip init complete\r\n");
char * buffer=pvPortMalloc(100);

while(gnetif.ip_addr.addr==0) osDelay(1);//wait the ip to reach the structure
printf("OUR Static ip adress:%s\r\n",ip4addr_ntoa(&gnetif.ip_addr));
local_ip =gnetif.ip_addr;
ip4addr_aton ("",&remote_ip);
conn=netconn_new(NETCONN_TCP);//create new network connection TCP TYPE
if (conn!=NULL)
/* Bind connection to well known port number 23 */
err = netconn_bind(conn,&local_ip,23);

if (err == ERR_OK)
/* Tell connection to go into listening mode. */
/* Infinite loop */
while (1)

/* Grab new connection. */
accept_err = netconn_accept(conn, &newconn);

/* Process the new connection. */
if (accept_err == ERR_OK)/* block until we get an incoming connection */
while (( recv_err = netconn_recv(newconn, &buf)) == ERR_OK)
netbuf_data(buf, &data, &len);
// netbuf_copy(buf,data,len);//not trustable much

printf("Received %d bytes:\r\n %s\r\n",len,data);
// printf("Received %d bytes:\r\n",len);
// for (i=0;i<len;i++)
// {
// printf("%c",data[i]);
// }
sprintf(buffer,"ack from stm\n\r");
netconn_write(newconn,buffer,strlen(buffer),NETCONN_COPY);//send ack
//netconn_write(newconn, data, len, NETCONN_COPY);//send same msg to client
HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_14);//blink a led to check if the prgm is keeping running

while (netbuf_next(buf) >= 0);
netbuf_delete(buf);//delete the recieved data


/* Close connection and discard connection identifier. */
// netconn_close(newconn);
// netconn_delete(newconn);


printf(" can not bind TCP netconn");
printf("can not create TCP netconn");


i need to read this way 

printf("Received %d bytes:\r\n",len);
for (i=0;i<len;i++)
printf("%c",data[i]); --------> but this one is not accepted (error of compile) i want to process or extract byte by byte data how should i write it ????


thanks much