Length encoded PDL

[Todd Lundstedt]

Is there an existing PDL, or has anyone already invented this wheel?

We are connecting to a vendor that requires a header instead of MLLP for record identification.  The header is:

Code:

byte 1: Message Type: D = Data, A = Ack, N = Nak, P = Poll (Polls are keep alive msgs)
bytes 2-6: Message Length: Length does not include header length
bytes 7-11: Message Transaction ID: Used to correlate Ack/Nak with original Data message

I am a PDL newbie, so if there is a PDL that exists that will accomplish this, delivered or custom coded, I would sure appreciate getting a hold of that.

Otherwise, it’s off to reading the PDL for Dummies manuals.

Thanks in advance.

Topic

[Jim Kosloskey]

Todd,

Ask the venodr if he can do length encoded TCP/IP. If so there is no PDL required.

But I am guessing you will want some Tcl to manage the header anyway.

Sounds like a vendor that has yet to leave the Bi-Synch communication days behind.

What your vendor describes is not an encapsulation technique but rather simply a message header.

If he cannot do length encoded, then I don’t think PDL will work for you without an end of message encapsulation. So I think you and the vendor will need to agree on what exactly will delineate the message – and if the vendor does not have an end of message delineator then he might need to add one – so why not just do length encoded?

AND A text based encapsulation is risky because the text pattern could be imbedded in the message itself causing misinterpretation of the message – the dreaded ‘no more phrases’ log entry.

email: jim.kosloskey@jim-kosloskey.com

[Todd Lundstedt]

Jim,

Am I understanding your post… PDL doesn’t work without a closing character for encapsulation?

The tcp_acknak pdl phrase doesn’t appear to have an end of message encapsulation, if I am reading it correctly:

Code:

define phrase basic-msg;
   field msglen = fixed-array( 4, any );
   length-encoded { encoding:network(bytes:4), store-in: msglen } =
       begin
           field data = variable-array( any );
       end;
end phrase;

[Jim Kosloskey]

Todd,

I believe that pdl is for handling a length encoded message.

The inbound message still needs to have the length encoding attached.

I see no reason to use a pdl when the tcp/ip protocol in the NetConfig will recognize and handle the length encoding if it is there.

Your vendor will still need to provide length encoding or true encapsulation I think.

email: jim.kosloskey@jim-kosloskey.com

[Michael Hertel]

Todd,

Here’s a pdl that we use on our rad flat results interface:

/* $Id: idxrad.pdl,v 1.3 1998/02/21 00:05:27 neuts Exp $ */
/*
* idxrad.pdl – Flat record protocol for results
*/

define driver idxrad;
[code]/* $Id: idxrad.pdl,v 1.3 1998/02/21 00:05:27 neuts Exp $ */
/*
* idxrad.pdl – Flat record protocol for results
*/

define driver idxrad;

[Michael Hertel]

Here is a copy of the tclproc we use for an example for you.

There is startup/shutdown stuff that may be helpful.

Code:

######################################################################
# Name: rad_shake
# Purpose:
# UPoC type: tps
# Args: tps keyedlist containing the following keys:
#       MODE    run mode (”start”, “run” or “time”)
#       MSGID   message handle
#       ARGS    user-supplied arguments:
#              
#
# Returns: tps disposition list:
#          
#

proc rad_shake {args} {
   keylget args MODE mode
   global HciSite HciConnName HciProcessesDir
   set module “$HciSite/$HciConnName/rad_shake: ”
   set ctrfile radidxctr
   
   if {[file exists $ctrfile.ctr] == 1} {
#echo “$module Using counterfile $ctrfile…”
#echo [pwd]
#echo $HciProcessesDir
   } else {
echo “$module Initializing counterfile ‘$ctrfile’…”
CtrInitCounter $ctrfile file 1 99999 1
   }

   set dispList {}

   switch -exact — $mode {
       start {
# Perform special init functions
# N.B.: there may or may not be a MSGID key in args
       }

       run {

keylget args MSGID mh
set msg [msgget -cvtnull _ $mh]

switch -exact — $msg {
“START-UP XXXX” {
append msg “V0000     ”
set response [msgcreate Y$msg]
lappend dispList “KILL $mh” “OVER $response”
}

“SHUTDOWN XXXX” {
append msg ”          ”
set response [msgcreate Y$msg]
lappend dispList “KILL $mh” “OVER $response”
}

default {
set dstring [clock format [clock seconds] -format %y%m%d%H%M%S]00
set response [msgcreate “Y[string range $msg 0 12]          “]
if {[crange $msg 13 13] == “R” && [msglength $mh] == 166} {
msgset $mh [strsub $msg 56 73 [rad_dr_n2a [crange $msg 56 61]][rad_dr_n2a [crange $msg 62 67]][rad_dr_n2a [crange $msg 68 73]]]
}
msginsert $mh “[crange [expr 100000 + [CtrNextValue $ctrfile]] 1 end] [crange $dstring 0 5] [crange $dstring 6 13]”

#kill test patients with MRN beginning with 8-88-8 per WR 61688
if {[crange $msg 14 14] == “D” || [crange $msg 14 19] == “8-88-8″} {
lappend dispList “KILL $mh” “OVER $response”
} else {
lappend dispList “CONTINUE $mh” “OVER $response”
}
}
}
       }

       time {
# Timer-based processing
# N.B.: there may or may not be a MSGID key in args
       }

       shutdown {
# Doing some clean-up work
       }

       default {
   error “$module Unknown mode ‘$mode'”
       }
   }

   return $dispList
}

[Author]

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