UDP Broadcast

Controllers Smoothie
1

Good morning,

i need to find one ore more smoothieboards (all set to DHCP) in a network. This is a Class B network, therefore an active TCP port scan is not a good idea.

For the Arduinos in the same network i implemented an UDP broadcast, the Arduinos simply answer with some ID string whenever they see a specific UDP packet on a specific UDP port. This was very easy to implement, around 8 lines of source code.

Now i want to implement the same feature in Smoothieware, but i have no idea where to start. I got the source code from github, it compiled OK and the Smoothieboard booted OK with my binary. So i’m all set for the source code changes, but where ?

Any suggestion to put me on the right track is welcome.

Thank You very much,

Christof

Imported from wikidot

2

Hey.

You want to look in https://github.com/Smoothieware/Smoothieware/tree/edge/src/libs/Network
Sorry for the short answer I’m in a hurry. Don’t hesitate to ask if you have questions.

Cheers.

3

I digged through the source code and as far as i understand all UDP packets go to

dhcpc_appcall in src\libs\Network\uip\dhcpc\dhcpc.c

due to

#define UIP_UDP_APPCALL dhcpc_appcall

then to

handle_dhcp

where i inserted some code after the promising comment with “some other UDP packet”

            // we may have gotten some other UDP packet in which case just wait some more for the right packet
            if (uip_newdata()) {
                if (parse_msg() == DHCPOFFER) {
                    s.state = STATE_OFFER_RECEIVED;
                    break;
                } else {
                    uip_ipaddr_t          rIP;
                     struct uip_udp_conn * pConn;

                rIP[0] = uip_conn->ripaddr[0];                     
                rIP[1] = uip_conn->ripaddr[1];                     

                pConn = uip_udp_new (& rIP, HTONS (4713));

                // MAYBE A BROADCAST PACKET TO DETECT US?  

                uip_udp_send (4);
                uip_udp_remove (pConn);
            }
        }</code>

I don’t check the source port at the moment and i don’t prepare the send buffer, i just want to get any reaction at all. But nothing.

I don’t understand where i should enter something to listen to my port (4712 in my case, will be an officially assigned one later).

Christof
4

I personally don’t think I can help you with this. If you read the code enough you should be able to figure it out.

5

It is now working. I needed to enhance the UIP part a little bit and i’m sure it’s not the optimal solution, but for my needs it’s OK. If anyone is interested i can supply my changes.

Best Regards,

Christof

6

I’m currently working on UDP communications (just receiving simple messages) and would be interested in what you had to change/add.