sockets

[Mark Bush]

I've been trying to get an application running and decided that the most
suitable implementation would be using broadcasting over datagram sockets.
I've produced client/server programs that communicated via sockets before
but then the client process connected to a server running on a specified
host.  I now want to access information in general across a network.
(I'm using Sun3s running SunOS 3.5)

The first step...RTFM:
>From "Networking on the Sun Workstation", "IPC Primer":

        To send a broadcast message, an Internet datagram socket should
        be created.

Nothing could be easier.

        and at least a port number should be bound to the socket.

Again, this is clear and straightforward.

        Then the message should be addressed as:

        dst.sin_family = AF_INET;
        inet_makeaddr(net, INADDR_ANY);
        dst.sin_port = DESTPORT;

Say what?  

I can find out what value `net' should be, no problem...this is well
documented, but doesn't `inet_makeaddr()' return an address?  Well, needless
to say, I tried what they said and got nothing.  Perhaps that line should
have said something like:

        dst.sin_addr = inet_makeaddr(net, INADDR_ANY);

I tried that, too.  Low and behold I actually managed to get

        sendto(s, buf, buflen, 0, &dst, sizeof(dst));

to return the same value as buflen!!!  What I want to know is: where did
it go?  My server process is continually `polling' its port...in fact it
does a `recvfrom' on its port (DESTPORT) and never returns.  I get the
feeling that I'm doing something grossly stupid, but what??!!!??

Mark Bush                      bush%uk.ac.oxford.prg at ac.uk
Teaching Support Programmer    bush%prg.oxford.ac.uk at nsfnet-relay.ac.uk
OUCL                           ...!uunet!mcvax!ukc!ox-prg!bush