[aprssig] aprsd drops mic-e characters

AE5PL Lists HamLists at ametx.com
Sat May 7 10:20:34 EDT 2005

> -----Original Message-----
> From: Tapio Sokura
> Posted At: Saturday, May 07, 2005 8:48 AM
> Subject: Re: [aprssig] aprsd drops mic-e characters
> Ok. Then what do I do to packets that contain cr, lf or any 
> combination of those anywhere in the packet? If I just 
> blindly pass packets containing them into the APRS-IS, they 
> will probably be mishandled. What I need is a clear and 

Actually, this is not a valid assumption.  The basis for APRS-IS is that
every line (note I did not say packet) conforms to either the TNC2 or
AEA monitor format.  The lines are terminated by CR and/or LF (CR and LF
is preferred).  If a packet is gated containing a CR or LF, it will be
passed up to the CR/LF.  Everything after the CR/LF will be ignored as
it would not conform to the TNC2/AEA format.

javAPRSSrvr does not modify, IN ANY WAY, the I-Field data.  In essence,
APRS-IS servers are packet switches and as such should NEVER modify the
payload of the packet.  It is wrong to assume that it is "ok" to strip
trailing spaces, white space, etc. as your software would then be
purposefully modifying the I-Field.  Just because errant
software/hardware may do this does not make it something to design to.

javAPRSSrvr does do extensive duplicate checking and has significant
built-in dupe checking for "mangled" packets.  It also cleans the header
to compensate for poorly configured TNC's and IGate software.  But it
does not modify the I-Field.

More information on this can be found at http://www.aprs-is.net and


Pete Loveall AE5PL
mailto:pete at ae5pl.net 

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