Manual

Data Communication and Host Modes
Rev 3.0B Feb.08 68
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PinPointXwill
continuetosendthisdata
(bufferinganyreceiveddatainthe
meantime)untilitreceivesanacknowledgementwiththis
sequencenumber.Ifanacknowledgementisnotreceived
withinthetime‐outperiod(specifiedinS7),thedatawillbe
retransmitted.Thiswillcontinueuntilanacknowledgementis
receivedorthe modemisreset.Likewiseany
UDPpackets
receivedbythePinPointXareexpectedtohavethissimple
header.ThePinPointXwillissueanacknowledgementforany
validpacketswhicharereceived.
ToconfigurethePinPointXforanormalUDPsession,you
needtosettheStartup ModeDefaultto73(ATMD73).Ifyou
areusingtwomodems,configuretheDestinationIPandPort
ineachtopointtoeachother.Serialdatawillthenbesent
reliablybetweenthetwo.
Caution: Although it adds reliability, the simple implementation of the
Reliable UDP mode in the does not check for duplicate packets.