Subject: Use of the PKT_ packet type definitions

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I have seen some students attempt to use

    90 #define PKT_CONNECT    0
    91 #define PKT_CONNACK    1
    92 #define PKT_DATA       2      // or ACK
    93 #define PKT_CLOSE      3
    94 #define PKT_CLOSEACK   4
    95 #define PKT_RESET      5
    96 #define PKT_TYPES      (PKT_RESET+1)

in an incorrect way.  The common error is to compare
them directly to hdr->flags as in:

    if (hdr->flags == PKT_CONNECT)
       do something

This can't possibly work!!!!  In a proper
connect packet hdr->flags == 1 . In a proper
connack packet hdr->flags == 3!!!

If you want to use the PKT_ defines you MUST
build a helper routine that maps flag settings
to PKT_ values:


    pkt = rps_packet_type(hdr->flags);
    if (pkt == PKT_CONNECT)
       do_something

The only USEFUL reason for using the PKT values
is if you use the table driven state machine
(described in the multicolored tables in the notes)
to drive your receive logic.

If you are not doing that you should work directly
with the RPH values as in

     if (hdr->flags == (RPH_CONNECT | RPH_ACK))
        dprintf("this is a connack packet \n");