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From: cerr on 2 Feb 2010 13:55
Hi There,

I would like to send a UDP broadcast datagram to all my network peers.
I've tried using following code:
struct sockaddr_in addr;
int BrdcstSock;
string message = "Hello, World!";

if ((BrdcstSock = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
std::cerr << "PIDClient: Error creating socket.\n";
return;
}

/* set up destination address */
memset(&addr,0x00,sizeof(addr));

addr.sin_family = AF_INET;

addr.sin_addr.s_addr = inet_addr("192.168.101.255");
addr.sin_port=htons(6767);
while (1) {
if (sendto(BrdcstSock, message.c_str(), strlen(message.c_str()), 0,
(struct sockaddr *) &addr, sizeof(addr)) != message.size()){
cout << "Error:" << strerror(errno) << endl;
return;
}
else
{
cout << "sent:" << message << endl;
}
sleep(3);
}
However, I do not see these packets with Wireshark and neither am I
seeing an error on the shell but i properly see "sent: Hello, World!"
appearing... :(
What's going on here, any clues?
Thanks for hints and suggestions!
--
roN
From: David Schwartz on 2 Feb 2010 14:16
On Feb 2, 10:55 am, cerr <ron.egg...(a)gmail.com> wrote:

> However, I do not see these packets with Wireshark and neither am I
> seeing an error on the shell but i properly see "sent: Hello, World!"
> appearing... :(
> What's going on here, any clues?

You forgot to enable broadcasts. For all the system knows, your
program selected a broadcast address accidentally (or worse, was
maliciously duped into doing so). Punch 'SO_BROADCAST' into your
favorite search engine.

DS
From: cerr on 2 Feb 2010 14:38
On Feb 2, 11:16 am, David Schwartz <dav...(a)webmaster.com> wrote:
> On Feb 2, 10:55 am, cerr <ron.egg...(a)gmail.com> wrote:
>
> > However, I do not see these packets with Wireshark and neither am I
> > seeing an error on the shell but i properly see "sent: Hello, World!"
> > appearing... :(
> > What's going on here, any clues?
>
> You forgot to enable broadcasts. For all the system knows, your
> program selected a broadcast address accidentally (or worse, was
> maliciously duped into doing so). Punch 'SO_BROADCAST' into your
> favorite search engine.
>
> DS

Thanks David,

I've done that. Ended up putting follwing after my socket creation:
if(setsockopt(BrdcstSock,SOL_SOCKET,SO_BROADCAST,&opt,sizeof(opt))){
cout << "Error setsockopt():" << strerror(errno) << endl;
return;
}
No change tho :(
still can't see anything with Wireshark :o (yes, filters are turned
off ;) )
Any other ideas?
From: Ersek, Laszlo on 2 Feb 2010 15:05
In article <31074a8e-344d-41a8-a71a-996fe5e7593e(a)y7g2000prc.googlegroups.com>, cerr <ron.eggler(a)gmail.com> writes:

> I've done that. Ended up putting follwing after my socket creation:
> if(setsockopt(BrdcstSock,SOL_SOCKET,SO_BROADCAST,&opt,sizeof(opt))){
> cout << "Error setsockopt():" << strerror(errno) << endl;
> return;
> }

1. Did you set "opt" to a nonzero value first?

2. Diagnostics should rather go to stderr or cerr.

3. Do *not* google. Choose a version of the SUS for the project and
stick to it.

http://www.opengroup.org/onlinepubs/007908775/xns/setsockopt.html
http://www.opengroup.org/onlinepubs/000095399/functions/setsockopt.html
http://www.opengroup.org/onlinepubs/9699919799/functions/setsockopt.html

All of SUSv2, SUSv3, SUSv4 are made available as tarballs.

http://www.opengroup.org/onlinepubs/007908775/download/
http://www.opengroup.org/onlinepubs/000095399/download/
http://www.opengroup.org/onlinepubs/9699919799/download/

Extract them onto your hard disk, and index them with one of the many
desktop search programs (or write a simple one yourself).

Cheers,
lacos
From: cerr on 2 Feb 2010 16:18
On Feb 2, 12:05 pm, la...(a)ludens.elte.hu (Ersek, Laszlo) wrote:
> In article <31074a8e-344d-41a8-a71a-996fe5e75...(a)y7g2000prc.googlegroups.com>, cerr <ron.egg...(a)gmail.com> writes:
>
> > I've done that. Ended up putting follwing after my socket creation:
> > if(setsockopt(BrdcstSock,SOL_SOCKET,SO_BROADCAST,&opt,sizeof(opt))){
> >       cout << "Error setsockopt():" << strerror(errno) << endl;
> >       return;
> >   }
>
> 1. Did you set "opt" to a nonzero value first?

Yes, sorry didn't paste that, i have defined opt like:
int opt=1;
>
> 2. Diagnostics should rather go to stderr or cerr.

Right, i can change that but would not change anything on the actual
problem, eh?
>
> 3. Do *not* google. Choose a version of the SUS for the project and
> stick to it.

I actually did look at the man page but also googled for a solution...
[snip]

> Extract them onto your hard disk, and index them with one of the many
> desktop search programs (or write a simple one yourself).

Yep, thanks :)

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