question: public static SnmpEngineId createEngineId ( InetAddress addr , int port , int iana ) { if ( addr == null ) throw new IllegalArgumentException ( "InetAddress is null." ) ; byte [ ] address = addr . getAddress ( ) ; byte [ ] engineid = new byte [ 9 + address . length ] ; engineid [ 0 ] = ( byte ) ( ( iana & 0xFF000000 ) > > 24 ) ; engineid [ 0 ] |= 0x80 ; engineid [ 1 ] = ( byte ) ( ( iana & 0x00FF0000 ) > > 16 ) ; engineid [ 2 ] = ( byte ) ( ( iana & 0x0000FF00 ) > > 8 ) ; engineid [ 3 ] = ( byte ) ( iana & 0x000000FF ) ; engineid [ 4 ] = 0x05 ; if ( address . length == 4 ) engineid [ 4 ] = 0x01 ; if ( address . length == 16 ) engineid [ 4 ] = 0x02 ; for ( int i = 0 ; i < address . length ; i ++ ) { engineid [ i + 5 ] = address [ i ] ; } engineid [ 5 + address . length ] = ( byte ) ( ( port & 0xFF000000 ) > > 24 ) ; engineid [ 6 + address . length ] = ( byte ) ( ( port & 0x00FF0000 ) > > 16 ) ; engineid [ 7 + address . length ] = ( byte ) ( ( port & 0x0000FF00 ) > > 8 ) ; engineid [ 8 + address . length ] = ( byte ) ( port & 0x000000FF ) ; return new SnmpEngineId ( engineid ) ; }
target:  Generates a unique engine Id. The engine Id unicity is based on the host IP address and port. The IP address is the passed one, it handles IPv4 and IPv6 hosts. The creation algorithm uses the passed IANA number.