STM32F429ZI freezes with FreeRTOS and LWIP UDP when both send and received are used

Hello,

I'm using a NUCLEO144 board. I've enabled FREERTOS and LWIP.

I have:

• one thread in charge of endlessly sending (netconn_sendto) out a message to a distant host and sleeps for a second osDelay(1000)
• a second thread in charge of receiving data from the network, it binds to a specific port and endlessly try to read something from the network (netconn_recv)

From a host on the network, I:

• Ping the card
• I have a listener who displays the messages sent by the sending thread
• I can send messages to the board.

Everything is working fine except when I send 2 messages.

The first one is sent fine, the second one freezes the board:

• it does no longer answer ping,
• it stops sending messages

I should have missed something could anyone help please?

thread start:

 /* init code for LWIP */
 MX_LWIP_Init();
 
 /* USER CODE BEGIN 5 */
 conn = netconn_new(NETCONN_UDP);
 netconn_bind(conn, IP_ADDR_ANY, 1700);
 LWIP_ERROR("udpecho: invalid conn", (conn != NULL), return;);
 
 osThreadDef(udpSrvTask, udpSrvTask, osPriorityNormal, 0, 128);
 udpSrvTaskHandle = osThreadCreate(osThread(udpSrvTask), NULL);
 
 osThreadDef(udpWriterTask, udpWriterTask, osPriorityNormal, 0, 128);
 udpWriterTaskHandle = osThreadCreate(osThread(udpWriterTask), NULL);

sender thread:

void udpWriterTask(void const * argument)
{
//	 struct netconn *conn;
	 struct netbuf *tx_buf;
	 err_t err;
	 char *adr;
	 LWIP_UNUSED_ARG(argument);
 char cString[ 50 ];
	 uint32_t ulCount = 0UL;
	 uint32_t dest = inet_addr( "192.168.20.112" );
	 u16_t lgMsg;
 
//	 conn = netconn_new(NETCONN_UDP);
//	 netconn_bind(conn, IP_ADDR_ANY, 1700);
//	 LWIP_ERROR("udpecho: invalid conn", (conn != NULL), return;);
 
	 while (1)
	 {
	 tx_buf = netbuf_new();
	 sprintf( cString, "Standard send message number %lu\r\n", ulCount );
	 lgMsg=strlen(cString);
	 netbuf_alloc(tx_buf, lgMsg);
 
	 LWIP_UNUSED_ARG(adr);
 
	 pbuf_take(tx_buf->p, (const void *)cString, lgMsg);
 
	 err = netconn_sendto(conn, tx_buf, (const ip_addr_t *)&(dest), 1700 );
	 if(err != ERR_OK) {
	 LWIP_DEBUGF(LWIP_DBG_ON, ("netconn_send failed: %d\n", (int)err));
	 } else {
	 LWIP_DEBUGF(LWIP_DBG_ON, ("got %s\n", buffer));
	 }
	 netbuf_delete(tx_buf);
 
	 ulCount++;
	 osDelay(1000);
	 }
 
}

receiver thread:

void udpSrvTask(void const * argument)
{
//	 struct netconn *conn;
	 struct netbuf *buf, *tx_buf;
	 err_t err;
	 char *adr;
	 LWIP_UNUSED_ARG(argument);
 
//	 conn = netconn_new(NETCONN_UDP);
//	 netconn_bind(conn, IP_ADDR_ANY, 1700);
//	 LWIP_ERROR("udpecho: invalid conn", (conn != NULL), return;);
 
	 while (1)
	 {
	 err = netconn_recv(conn, &buf);
	 if (err == ERR_OK)
	 {
		 adr=inet_ntoa(buf->addr);
	 }
	 netbuf_delete(buf);
	 }
 
}

struct netconn *conn;

is a global data, I previously included it in both thread, same result.