Changing IP address at runtime

Question

I am creating a tcp connection using the function socket(), bind(), and then listen().

Our customers would like to be able to define an IP address of the server at runtime. Is there a way of changing the IP at runtime or must it be done in the BIOS?

Thanks for any tips

Answer 1

I am not sure what you mean by defining 'IP address of the server at runtime?'. Obviously for a given socket it's IP address cannot be changed. It's an endpoint of a connection, it cannot be changed run time. If you just want to assign multiple IP addresses to a host that's possible.

In general - you can add as many IP addresses as you want to your machine (ok not exactly) but certainly a hundred or so (ie. statically allocated). That's not the problem (management of that is a nightmare, but sure not impossible). The problem is how those IP addresses are reached, that is not in your control, that depends upon the settings on client especially the routing entries. eg. you could use all of the IP addresses in a Subnet (say 10.1.2/24).

Not recommended - but possible.

Once you have those IP addresses - you bind on the port and address as INADDR_ANY, which says accept connection on 'any ' of the local addresses. On which address the connection was made to can be determined on server using getsockname.

Answer 2

I've changed the IP address using ifAddrSet(..) many times. Usually I call this function from within the startup script before my application is running so I have no idea how calling this function affects already connected sockets.

But have a look at the functions provided by ifLib.h. I'm sure you'll find something that suits your needs (ifAddrAdd(..) looks promising).