[lwip-users] How do I handle the ETHERNET cable unplug/replug on the server side using LWIP in a correct way?

[Hensel, Christian]

Hi there,

thanks for the information. I will try to narrow my question down to one point.

Let's assume the LWIP settings at the server are:

MEMP_NUM_UDP_PCB = 1
MEMP_NUM_TCP_PCB = 1

Meaning only one sock_connection is allowed to be served at any time

The code snipplet is

for(;;)
{
//
sock_connection = lwip_accept();

// will time out after 5 sec
lwip_select(sock_connection);

// read and handle is not shown here

//
lwip_shutdown(sock_connection, SHUT_RDWR);
lwip_closesocket(sock_connection);
}

The first connection attempt of the client is successful, so sock_connection is 
1
While in lwip_select the (physical cable) connection gets lost and no FIN or 
ACK is received by the server.

On the second connection attempt of the client lwip_select will be executed but 
returns -1.
And the client gets a TCP connection timeout.

How long will LWIP wait until the next sock_connection can be successfully 
established?
Which parameters need to be set to decrease this time?
Are there any other parameters to be set to get this working?

Thank You!

CLASSIFIED: CONFIDENTIAL

Christian Hensel
Project Engineer Software Development

PHONE +49 351 2637616
EMAIL Hensel.Christian@vonardenne.biz

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