How do Nios-II handle IP address change during the TCP/IP connection?

As far as I have seen, there is no need to call netmain_init().

Is there a reason why you are executing it?

If you disable DHCP in the BSP, there is no DHCP code in your project.

It is surrounded by -ifdef everywhere, and won't get included.

It will be better to change get_ip_addr(), and set use_dhcp = 0 there.

This function is there for customization, so that's the point to start.

I'm not sure this will do it, maybe one has to disable the NF_DHCPC flag (wherever that gets set; I have seen it already, but can't remember where).

To enable DHCP then, you can use my code as above.

The 3 times problem I have not seen yet, as I have just changed my IP Address 2 times: DHCP->static->DHCP.

I'll try tomorrow.