Re: [ECOS] limited broadcast IP

[Andrew Lunn <andrew at lunn dot ch>]

On Thu, Feb 23, 2006 at 11:17:32AM -0600, paape@Hi-Techniques.com wrote:
> Andrew,
> You've found about a quarter of a page more than me. 

TCP/IP Illustrated, Volume 1: The protocols. W. Richard Stevens.

Section 12.2, page 171.

> I have a foot in both
> the UNIX and Windows camps (and I'm not very comfortable with the Windows
> side).  Our product incorporates systems running both Windows and eCos.
> Right or wrong, the Windows part seems to send the type of packet that I'm
> describing, by default.  I have an eCos thread that receives it and responds
> directly to the sender.  So far so good.  Now, as part of this product, I
> will have other eCos systems that also need to query info from this first
> (eCos) system.  It however, does not appear to receive the subnet
> broadcast.

Try this code. It should receive broadcast packets sent to port 4567.

  int sock, err;
  struct sockaddr_in addr;
  char buffer[64];
  wlink_msg_t msg;
  int one = 1;

  sock = socket(AF_INET, SOCK_DGRAM, 0);
  if (sock == -1) {
    perror("socket");
    exit(-1);
  }

  memset(&addr, 0, sizeof(addr));
  addr.sin_family = AF_INET;
  addr.sin_port = htons(4567);
  addr.sin_addr.s_addr = INADDR_ANY;

  err= setsockopt(sock, SOL_SOCKET, SO_BROADCAST,&one, sizeof(one));
  if (err == -1) {
    perror("setsockopt(SO_BROADCAST,1)");
    exit(-1);
  }

  err= setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,&one, sizeof(one));
  if (err == -1) {
    perror("setsockopt(SO_REUSEADDR,1)");
    exit(-1);
  }
  err = bind(sock, (struct sockaddr *)&addr, sizeof(addr));
  if (err == -1) {
    perror("bind()");
    exit(-1);
  }

  while(1) {
    err = recvfrom(sock, buffer, sizeof(buffer),0, NULL, 0);
    if (err < 0) {
      perror("read()ing from socket");
      exit(-1);
    }

    memcpy((char *)&msg.dst, &buffer[2],32);

I've only tested this on Linux....

        Andrew

-- 
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss