[lwip-users] TCP server disconnection issue

[Michal Timm]

Hello,

I have got issue with TCP server disconnection.

Version: lwip-2.1.2
Code: Pattern I am working with:

/* TCP connection setup
*/
structnetconn*conn, *newconn;
err_terr = ERR_OK;
conn = netconn_new( NETCONN_TCP);
err = netconn_bind( conn, &ipAddr,
tcpPort);
netconn_listen( conn );

for(
;; )
{
    /*
Grab new connection */
    err = netconn_accept(conn,
&newconn);

    /*
Process the new connection */
    if(err == ERR_OK)
    {
        while( err == ERR_OK)
        {
           
structnetbuf*rxBuf = NULL;
           
err = netconn_recv( newconn, &rxBuf );

           
/* Continuously get data
requests from TCP Client and send response */
           
do
           
{
           
    /* Get
data from netbuf */
           
    netbuf_data(rxBuf, &requestReceived, &reqLength);

           
    /* Prepare
transmit buffer */
           
    structnetbuf*
txBuf;
           
    txBuf = netbuf_new();
           
    (void)netbuf_alloc(
txBuf, MB_MAX_MESSAGE_LENGTH );

           
    /* Analyze
request and prepare response 
       
         *
       
         */

           
    err = netconn_write( newconn, txBuf->p->payload,
rspLength, NETCONN_COPY );

           
    /* Delete
transmit buffer */
           
    netbuf_delete( txBuf );
           
}
           
while( ( err == ERR_OK) && (netbuf_next( rxBuf ) >= 0 ) );

           
/* Delete receive buffer
*/
           
netbuf_delete( rxBuf );
         }
    }

    if( newconn != NULL )
    {
        netconn_close(
newconn );
        netconn_delete(
newconn );
    }
    vTaskDelay( pdMS_TO_TICKS(
TRY_RECONNECT_TIME ) );
}


Server app (lwip) is a part of embedded
system.
TCP Client Test application is running
on my PC.
There are 2 ways of disconnection which
I have tested:

CASE 1. Turn off Client application
(cable between my PC and embedded system remain connected).
Registered errors:
ERR_CONN/**
Not connected.           */or
ERR_RST/**
Connection reset.        */or
ERR_CLSD/**
Connection closed.       */
Resources were properly freed. In lwip_stats.memp[0]
(MEMP_TCP_PCB)) was decreased by 1.
I can make new connection by run Client
application on PC and connection is being established. Everything works
fine.

CASE 2. Disconnect eth cable by removing
RJ45 connector.
Registered errors:
ERR_RTE/**
Routing problem.         */
Resources WERE NOT properly freed. In
lwip_stats.memp[0] (MEMP_TCP_PCB)) is on the same level as before
cable disconnection. I can make new connection but number of used resources
is increasing every time new connection is being established.


How can I handle cable disconnection
to achieve resource release as in case 1? 
Have you had similar issues?


Best Regards,
Michał Timm


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