UDP - Java Network Programming - page 437

channel . register ( selector , SelectionKey . OP_READ | SelectionKey . OP_WRITE );
ByteBuffer buffer = ByteBuffer . allocate ( 4 );
int n = 0 ;
int numbersRead = 0 ;
while ( true ) {
if ( numbersRead == LIMIT ) break ;
// wait one minute for a connection
selector . select ( 60000 );
Set < SelectionKey > readyKeys = selector . selectedKeys ();
if ( readyKeys . isEmpty () && n == LIMIT ) {
// All packets have been written and it doesn't look like any
// more are will arrive from the network
break ;
}
else {
Iterator < SelectionKey > iterator = readyKeys . iterator ();
while ( iterator . hasNext ()) {
SelectionKey key = ( SelectionKey ) iterator . next ();
iterator . remove ();
if ( key . isReadable ()) {
buffer . clear ();
channel . read ( buffer );
buffer . flip ();
int echo = buffer . getInt ();
System . out . println ( "Read: " + echo );
numbersRead ++;
}
if ( key . isWritable ()) {
buffer . clear ();
buffer . putInt ( n );
buffer . flip ();
channel . write ( buffer );
System . out . println ( "Wrote: " + n );
n ++;
if ( n == LIMIT ) {
// All packets have been written; switch to read-only mode
key . interestOps ( SelectionKey . OP_READ );
}
}
}
}
}
System . out . println ( "Echoed " + numbersRead + " out of " + LIMIT +
" sent" );
System . out . println ( "Success rate: " + 100.0 * numbersRead / LIMIT +
"%" );
} catch ( IOException ex ) {
System . err . println ( ex );
}
}
}