Re: [lwip-users] Handling sudden disappearance of network i/f

[Janusz U.]

> I think you misunderstand how TCP connections are closed.

you are right - i am still learning.

>  A FIN does
> not mean the connection is closed.  It just means that whoever sent it
> doesn't want to send any more data.  The connection is still open in the
> other direction, and it is perfectly valid (and quite normal) for one
> side to send a FIN, but the other end to still send data.  A connection
> is not closed until both applications close it.

yes, but if FIN is sent by serwer lwIP should return from netconn_recv and 
inform me about. Ather I can close the socket...

> I've just had a look at how FINs are processed in the case of the
> netconn API.  The core lwIP will call the raw API recv callback with a
> NULL buffer.  This will post NULL to the netconn API's recv mbox.  The
> netconn_recv() function, when it gets NULL from the mbox, returns a
> length of 0.  This is standard semantics for "there are no more data to
> read".

oh, thanks a lot! I thought about but I hoped recv return to me null buffer:
if ((getPPPstate() == pppCONNECTED) &&
 (inet_aton(userCfg.srv.name, &srv_ip_addr)) &&
 (userCfg.srv.port != 0)) {
 pxSRVconn = netconn_new(NETCONN_TCP);          // init conn
 if (pxSRVconn != NULL)
  if (pxSRVconn->pcb.tcp != NULL) {
   pxSRVconn->pcb.tcp->keepalive = 120000;        // set keepalive time in 
ms
   pxSRVconn->pcb.tcp->so_options |= SO_KEEPALIVE;      // turn on 
keep-alive
  }
 setSRVstate(srvCONNECTING);
 kprintf("SRV connecting\n");
 // start client-server connection
 if (netconn_connect(pxSRVconn, &srv_ip_addr, userCfg.srv.port) == ERR_OK) 
{ // open socket
  setSRVstate(srvCONNECTED);
  kprintf("SRV connected !!!!!!!!!!!!!!!!!!!!!!!\n");
  // data receiving loop
  while ((pxRxBuffer = netconn_recv(pxSRVconn)) != NULL) {
   kprintf("SRV recv\n");
   // get all data and send it into BT
   do {
    netbuf_data(pxRxBuffer, (void *) &pcRxString, &usLength);
    // debug
    /*
    kprintf("\n-START-\n");
    //for (i=0; i<usLength; i++) kprintf("%02x", pcRxString[i]);
    for (i=0; i<usLength; i++) kprintf("%c", pcRxString[i]);
    kprintf("\n-END-\n");
    */
    if (getBTstate() == btCONNECTED)
     comm_write(BT_DEV, pcRxString, usLength);
   } while (netbuf_next(pxRxBuffer) >= 0);
   netbuf_delete(pxRxBuffer);
  }
  netconn_close(pxSRVconn);            // close socket
 }
 setSRVstate(srvDISCONNECTED);
 kprintf("SRV disconnected\n");
 netconn_delete(pxSRVconn);             // done conn
} else vTaskDelay(50);               // unblock the task

should I check buffer len for the zero?

kind regards
Janusz