For the first question, you have to specify LocalAddr, that should resolve your problem. For example:

use IO::Socket::INET;

$sock_r = IO::Socket::INET->new(Proto => "udp", LocalAddr => "127.1")
                 or die "can't connect socket to port: $!";

    $host_port = $sock_r->sockport;
    print "Listening on host_port $host_port\n";
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For you second part, just as jasonk said UDP does not understand what ASCII is, or what binary is, it is just a stream of bytes. Encoding is controlled by your script. Absolutely nothing to with UDP, and UDP absolutely does not care that.

As for syntax, you write binary data to socket in the same way you swrite ascii data to it. The socket does not know, and does not care what you are sending.