User guide

Data Communication and Host Modes
Rev 3.0D Jul.09 63
WhentheRavenXTisinaTCPsession,allcharactersreceived
ontheserialportareassembledintoTCPpacketsandsentto
themodeʹsremoteIPaddress/port,andanypacketsreceived
fromtheremoteendoftheTCPconnectionaredisassembled
anddumpedontotheserialline.
ATCPconnectionisestablishedbyoneofthefollowing
methods:
• UsingtheDialTCP(DT)ATcommand.Forexample,
ATDT192.168.3.23/3456.
• TCPautoanswerisenabled(S1),aTCPconnectionrequest
isreceived,andthemodemisnotinadatasession.
• Dataisreceivedontheserialportand
· TheStartupModeDefault(MD)is4(autoTCP)
· TheremoteTCPdestination,asdefinedinS53,success‐
fullyrespondstotheTCPconnectionrequest.
ThevalueofS7(TCPConnectionTime‐out)specifiesthe
numberofsecondstowait,afterinitiatingaTCPconnection
attempt,forasuccessfulconnectiontobeestablished.Ifthe
connectionhasnotbeensuccessfullyestablishedbeforethe
time‐outoccurs,ERROR/BUSYisreturned.
TCPpacketassemblyisaffectedbythevaluesofS50(PAD
ForwardingTime‐out)andS51(PADForwardingCharacter).
Datareceivedintheserialbufferwillbetransmittedwhenthe
idleinter‐charactertime‐outspecifiedinS50(intenthsof
seconds)occursorwhenacharacterisreceivedthatmatches

S51(ifnon‐zero).
TheTCPsessionwillbeterminatedifnodataistransmittedor
receivedforthetimeintervalspecifiedinTCPTandTCPS.
TCPTisthenumberofminutes(TCPS=0)orseconds(TCPS=1)
usedforthisidletime‐out.
Caution: TCPT should never be 0 when using the TCP mode. A
broken TCP session can result in the modem being left with a TCP
TCP Auto Answer
TCPautoanswer(S0= 1|2)alsoallowsaTCPconnection
requesttobe“answered”whenthemodemisidle,notina
datasession.TheTCPconnectionrequestʹsdestinationport
hastomatchthemodemʹsdeviceport.
Note: UDP auto answer may also be set simultaneously with TCP
auto answer. Then, when in the idle state, the modem will accept
either a TCP connection request or UDP incoming packet, and enter a
TCP or UDP session as appropriate.