[lwip-users] Re: [lwip] Need a udp sample using raw interface

[John C. Toman]

Rajeev,

Your code to send a packet should look something like the following 
pseudocode (this works with lwIP 0.5.3 and I believe it's fine for later 
versions):

struct ip_addr *destination;
struct udp_pcb *pcb;
struct pbuf *p;
u16_t packet_size; // You need to determine how big your packet needs to be

p = pbuf_alloc(PBUF_TRANSPORT, packet_size, PBUF_RAM);

// Code omitted here would fill in your packet (for example, get 
p->payload and cast it to a structure)

// Open the port and send the data
pcb = udp_new();
udp_connect(pcb, destination, SERVER_PORT_YOU_ARE_CONNECTING_TO);
udp_send(pcb, p);

// Close the port
udp_remove(pdb);

Binding to receive data with the raw API is a little different, you've 
got to have a callback function (and don't close the pcb):

void
udp_callback_function(void *passed_data, struct udp_pcb *pcb, struct 
pbuf *p, struct ip_addr *addr, u16_t port)
{
    // Do something with the packet that was just received
}

// The rest here is pseudocode

void *passed_data = NULL;

udp_recv(pcb, udp_callback_function, passed_data);
udp_bind(pcb, IP_ADDR_ANY, PORT_I_WANT_TO_RECEIVE_DATA_ON);

Hope this helps,

John

Rajeev Nair wrote:

> Hi,
> I am partly getting success in porting lwip on WinCE. So far I have 
> ported the raw interface only. I would like to get hold of a udp 
> sample that sends udp datagrams using raw interface. Any 
> inputs/references/links will be of great help.
> thanks,
> regards
> rajeev
> [This message was sent through the lwip discussion list.]





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