Sierra Wireless 20070914

Data Communication and Host Modes

Rev 3.0B Feb.08 62

remoteIP/portuntilnodataissentorreceivedforthetime

intervaldefinedintheUDPautoanswertime‐out(S83).

Duringthissession,packetsfromotherIP/portaddresseswill

berejected,unless*UALLisset.Whetherornotanincoming

packetwillcausethemodemtoenteraUDPsessionisalways

dependentontheS53andAIPsettings.

TheNormalUDPMode(MD3)canbecombinedwithUDP

autoanswertocausetheincomingserialdatatobesentin

UDPpackets(insteadofbeingtreatedasATcommands),while

allowingsessionstobeestablishedfromdifferentUDP

sources.AUDPsessionwillbeinitiatedeitherbyincoming

serialdataorbyanincomingUDPpacket.Thesession,started

byeithermethod,willbeterminatedwhennodatahasbeen

sentorreceivedfortheS82period.Oncethesessiontermi‐

nates,anothermaybeinitiatedbyeithermeans.

Whenidle,afterthetime‐outhasoccurred,themodemisinAT

commandmodeontheserialport,andanyvalidATcommand

maybeenteredduringthistime.

Tip: It is best to ensure the idle time-outs for TCP and UDP are never

0 if you're going to be using auto-answer, or either PAD mode. In

those circumstances, you will want the modem to close the socket if

the connection goes idle for too long, particularly if the other side

doesn’t normally close the connection.

Whenthesessionisinitiatedbyserialdata,thenewsession

willbeestablishedusingthedestinationaddressspecifiedin

S53.TheS53settingcanbechangediftheconnecttolastUDP

setting(*UDPLAST=1)isset.TheaddressinS53willbe

updatedtoreflecttheaddressofthelastsessioninitiatedbyan

incomingUDPpacket.Sothatwhennewdataisreceivedover

thehostserialportwhileintheidlestate,asessionwillbere‐

establishedwiththelastaddress.(Thisbehavioristhesameas

thepreviousHybrid2(MD6)mode).

Tip: TCP auto answer (S0) may also be set simultaneously with UDP

auto answer. Then, when in the idle state, the modem will accept

either a TCP or UDP incoming packet, and enter a TCP or UDP

session as appropriate.

Reliable UDP

ReliableUDPaddsasimpleprotocolontopofUDPtoprovide

reliabledeliveryofdata.Whendataisreceivedfromthehost

serialport,a2byteheaderisaddedtothedata,containinga

messagetypeandasequencenumber.TheRavenwillcontinue

tosendthisdata(bufferinganyreceiveddatainthemeantime)