[lwip-users] Handling dead TCP connection

[Thomas Johansen]

Hi All

How do I handle dead TCP connection best in lwIP?

It is not always detected by the stack that the connection is lost.
So therefore we have a high level keep alive.

In cases of failed keep alive I do a netconn_disconnect(xNetConn) and then a 
netconn_close(xNetConn), before I try reconnect.


If I kill the TCP listen server (PC application), I get an error  -11 
(connection reset) ot -12 (Connection close) depending on how I close it.
I then call netconn_close(xNetConn) netconn_delete(xNetConn).
Then I invalidate the net connection (xNetConn = NULL ) and start binding again.

I the sometime get and LWIP asset: IP.c linie 755

/* pbufs passed to IP must have a ref-count of 1 as their payload pointer
     gets altered as the packet is passed down the stack */
  LWIP_ASSERT("p->ref == 1", p->ref == 1);


I If just do a netconn_delete(xNetConn) and then I try reconnect I get a 
hardfault.

I guess I'm asking for any "best practice" on how to handle TCP connection 
error from lwIP and how to handle them lwIP style.
(delete, close, bind etc combination)

Thomas Johansen

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