Easy GPRS User Guide
Contents
1. The Easy GPRS feature provides a way to accept incoming TCP UDP connections and keep the same IP address after a connection leaving the GPRS context active The steps that will be reguired to open a socket in listen waiting for connection reguests from remote hosts and accept these reguest connections only from a selected set of hosts then close it without closing the GRPS context are configuring the GPRS Access configuring the embedded TCP IP stack behaviour see par 2 1 1 2 defining the Internet Peer that can contact this device firewall settings see par 2 1 2 1 reguest the GPRS context to be activated see par 2 1 1 4 reguest the socket connection to be opened in listen see par 2 1 2 2 receive connection requests see par 2 1 2 3 exchange data close the TCP connection while keeping the GPRS active see par 2 1 1 6 All these steps are achieved through AT commands As for common modem interface two logical statuses are involved command mode and data traffic mode e n Command Mode CM some AT commands are provided to configure the Data Module Internet stack and to start up the data traffic e In data traffic mode Socket Mode SKTM the client can send receive a raw data stream which will be encapsulated in the previously configured TCP IP packets which will be sent to the other side of the network and vice versa Control plane of ongoing socket connection is deployed internally to the module 2 1 2 1 Defini2. DSTO e the socket inactivity timeout see command SKTTO 2 1 1 3 Saving settings for the Internet peer to be contacted In order to maintain all settings for TCP IP stack refer to the AT command SKTSAV that saves the actual socket parameters in the NVM of the device page 17 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 2 1 1 4 Reguest the GPRS context to be activated With the command GPRS you can activate or deactivate a GPRS context INDEPENDENTLY from the TCP socket opening AT GPRS 1 activates the context AT GPRS 0 deactivates the context Therefore with the ATGPRS 1 command the module e Telit module activates the context previously defined with AT CGDCONT e Telit module proceeds to the authentication with the parameters specified Note that activating a context implies getting an IP address from the network and this will be maintained throughout the session The response code to the ATZGPRS 1 command reports the IP address obtained from the network allowing the user to report it to his server or application Deactivating the context implies freeing the network resources previously allocated to the device 2 1 1 5 Open the connection with the internet host With the AT command SKTD socket Dial the TCP UDP request to connect with the internet host starts e DNS query is done to resolve the IP address of the host name internet peer e Telit module establishes a TCP UDP depending on
3. ccu tna RON FREU RES HT PAN JD Flecraauction forbidden without Telit Communications S p A written authorization All Rights Reserved page 3 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 1 GPRS Operations 1 1 Introduction The General Packet Radio Services GPRS standard permits DATA transfers in a completely different way with respect to previous point to point communications made with Circuit Switch Data CSD GSM modems In CSD operations the modem establishes a connection with the other party another modem in such a way that all the Network devices in between are transparent to the data exchanged simulating a real point to point connection just as if the other party is directly connected with the controlling application of the modem The other party can be either an Internet Service Provider ISP or a private server but in any case the arrival point must have a modem to connect to Landline ISDN or GSM CSD The connection establishment procedure defines a particular path where all the information exchanged between the two peers flows and this path is reserved for exclusive use of these 2 peers for all the time the connection is active This approach has the drawbacks of a long time to set up the link between the two peers up to a minute and a time counting bill which proceeds even if no data is exchanged because the path resources are reserved anyway furthermore the speed of the data transfer i
4. Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 0 subscribed default 1 delay class 1 2 delay class 2 3 delay class 3 4 delay class 4 best effort lt reliability gt is the connection reliability class It represents the connection reliability reguested the higher is the number the less reliable is the data exchanged 0 subscribed default 1 reliability class 1 acknowledged GTP LLC and RLC protected data 2 reliability class 2 unacknowledged GTP acknowledged LLC and RLC protected data 3 reliability class 3 unacknowledged GTP and LLC acknowledged RLC protected data 4 reliability class 4 unacknowledged GTP LLC and RLC protected data 5 reliability class 5 unacknowledged GTP LLC and RLC unprotected data Pm peak is the peak data transfer throughput 0 subscribed default 1 up to 7 8 kbps 2 up to 15 6 kbps 3 up to 31 3 kbps 4 up to 62 5 kbps 5 up to 125 kbps 6 up to 250 kbps 7 up to 500 kbps 8 up to 1000 kbps 9 up to 2000 kbps means is the mean data transfer throughput 0 subscribed default 1 upto 0 8 kbps 2 upto 1 6 kbps 3 upto 3 9 kbps 4 upto 7 8 kbps 5 up to 15 6 kbps 6 up to 39 kbps 7 up to 78 kbps 8 up to 156 kbps 9 up to 390 kbps 10 up to 7 6 Mbps 11 up to 15 2 Mbps 12 up to 38 2 Mbps 13 up to 76 3 Mbps 14 up to 152 Mbps 15 up to 381 Mbps 16 up to 762 Mbps 17 up to 1525 Mbps 18 up to 3815 M
5. active mode default 1 passive mode In order to close the FTP connection the AT command AT FTPCLOSE should be used PEPIS forbidden without Telit Communications S p A written authorization All Rights Reserved page 22 of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 2 2 2 Setting the FTP Transfer Type With the command AT FTPTYPE lt type gt is possible to configure the file transfer type The command must be provided during an FTP connection Parameter lt type gt file transfer type 0 binary 1 ASCII NOTE The command causes an ERROR result code to be returned if no FTP connection has been opened yet NOTE If the parameter is omitted then the behaviour of Set command is the same of Read command 2 2 3 FTP File transfer to the server With the command AT FTPPUT lt filename gt to issued during an FTP connection is possible to open a data connection and starts sending lt filename gt file to the FTP server If the data connection succeeds a CONNECT indication is sent otherwise a NO CARRIER indication is sent Parameter lt filename gt string type name under which you choose to save the file on the server must have the right extension es if the file you re sending is txt then the lt filename gt can be test txt NOTE use the escape sequence to close the data connection NOTE The command causes an ERROR result code to be returned if no FTP connection has bee
6. com 194 185 15 65 by smtp5 libero it 7 0 027 DDO1 GUIT lt cr gt lt lf gt OK POP3 server closing connection NO CARRIER 2 3 4 Remote connection between two modules Configuration for the module that receives data server Define PDP Context AT4 CGDCONT 1 IP ibox tim it 0 0 0 0 GPRS Context Activation AT GPRS 1 Firewall Setup if requiered AT FRWL 1 198 158 1 1 0 0 0 0 Socket Listen AT SKTL 1 0 1024 255 First you have to define PDP context filling in the information of APN in this example ibox tim it Next step is activation of GPRS context which gives as reply the IP of the module assigned by network AT GPRS 1 IP 217 201 142 223 OK Before opening socket in listen it is possible to define an accept firewall chain in order to filter IP of the senders At the end with AT commad AT SKTL 1 0 1024 255 the socket will be set in listen on the port 1024 Configuration for the module that opens connection client alib Reproduction forbidden without Telit Communications S p A written authorization All Rights Ah page of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 Define PDP Context AT4CGDCONT lt 1 IP ibox tim it 0 0 0 0 GPRS Context Activation AT GPRS 1 Socket Dial AT SKTD 0 1024 217 201 142 223 First you have to define PDP context filling in the information of APN in this example ibox tim it Next step is activation of GPRS con
7. context to be written up to 5 different context Flecraauction forbidden without Telit Communications S p A written authorization All Rights Reserved page 11 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 lt precedence gt is the precedence class lt delay gt is the delay class lt reliability gt is the connection reliability class lt peak gt is the peak data transfer throughput means is the mean data transfer throughput Parameters assume the same values as in the previous section e wait for response Response Reason Action OK context parameters have been proceed ahead successfully stored ERROR some error occurred check parameters and retry For example 1 Let s assume you want to set up the GPRS context number 1 cid written before with your GPRS reguested OoS parameters Precedence class High priority Delay class subscribed Reliability class subscribed Peak throughput subscribed Mean throughput best effort command AT CGQREQ 1 1 0 0 0 31 cr response OK NOTE Telit suggests to setup AT CGQMIN 1 0 0 3 0 0 Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 12 of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 1 3 GPRS context activation and data state entering This operation corresponds to the dial and connect of a CSD GSM data call issued to an internet servi
8. the parameter request connection with the given internet host e Once the connection is up the module reports the code CONNECT NOTE all peer specifications of this socket Dial are within the command and not the one stored with SKTSET command From this moment the data incoming in the serial port is packet and sent to the Internet host while the data received from the host is serialised and flushed to the Terminal Equipment NOTE when disconnecting the SKTD command does not close the GPRS context leaving it active for next connections until an AT HGPRS 0 command is issued or the network requests a context closing 2 1 1 6 Close the Socket without deactivating the context The connection can be closed for the following reasons remote host TCP connection close socket inactivity timeout Terminal Equipment by issuing the escape sequence Network deactivation page 18 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 NOTE if there is an escape seguence in the raw data to be sent then the TE must work it out and sent it in a different fashion to guarantee that the connection is not closed The pause time is defined in the parameter S12 On the reception of an escape sequence if the socket was opened with the ATZSKTD command the Telit module closes the connection does not deactivate the GPRS context and returns to command mode issuing the NO CARRIER code 2 1 2 Easy GPRS Incoming Connection
9. PRS lt cr gt 2 Authentication setting AT PKTSZ 300 3 Socket setting AT DSTO 50 3 Socket setting AT SKTTO 90 3 Socket setting AT SKTCT 600 3 Socket setting wa Da Da a For our convenience we store all these parameters with the command AT SKTSAV lt cr gt Now we can activate the GPRS context AT GPRS 1 lt cr gt IP 193 199 234 255 OK The commands gives as response the IP address assigned to the module by the network AT SKTD 0 110 POP mail server 0 0 lt cr gt When we receive the CONNECT indication then we are exchanging data with the POP3 server program on the remote host machine Following the POP3 protocol we can proceed with the authentication directly over the serial line in blue you can find the data sent by us in violet the one received from host OK POP3 PROXY server ready 7 0 027 lt A6B4DDEA93433C73A01 pop4 libero it gt USER module 2domain com cr If Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 31 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 OK Password required PASS telit lt cr gt lt lf gt OK 1 messages LIST r n OK 1 19550 RETR 1 lt cr gt lt lf gt OK 19550 bytes Return Path lt module domain com gt Received from smtp5 libero it 193 70 192 55 by ims2d libero it 7 0 028 id 40DFC49A010E5708 for test libero it Tue 17 Aug 2004 12 24 02 0200 Received from smtp telital
10. Pd e leli wireless solutions Easy GPRS User Guide 80000ST 10028 Rev 0 02 01 07 A uou Wes LCS C n at 7 r4 oie T 5 L 4 wes Making machines talk Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 This document is relating to the following products GE863 GPS 3 990 250 660 GT863 PY 3 990 250 466 GM862 OUAD 3 990 250 655 GE863 OUAD Pb balls 3 990 250 664 GE864 QUAD 3 990 250 675 GM862 QUAD PY 3 990 250 656 GE863 PY Pb balls 3 990 250 665 GE864 PY 3990 250 676 GM862 OUAD 3 990 250 659 GE863 QUAD Pb free 3 990 250 653 GM862 OUAD PY 3 990 250 658 GE863 PY Pb free 3 990 250 654 GE863 QUAD Pb free 3 990 250 662 GE863 PY Pb free 3 990 250 661 GE863 QUAD 3 990 250 651 GE863 PY 3990 250 650 Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page TWE of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 Contents 1 GPRS Operations TT HENW CETA FFON NEF FERRE FF E RD ENNYD NEEDS m 4 LLLI 4CSD application ex mple 5 SERERE Bep RS el p e ER a plots 6 1 112 GPRS applicati n ex nmple neii uii du iog nuu GRY oL LCD FO GL DU CE UY UG Loreto spe YU 7 12 Preliminary GPRS context parameters Setting scsscssscssscscscsssescssccsscscscscsssessseccssccsscssscssses
11. Trasmission Control Protocol Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 Reproduction romidden without Telit Communications S p A written authorization All Rights page uu of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 4 Document Change Log Revision Date Changes ISSUE 0 02 01 2007 Initial release IL Tan I pi a os 8H s d ES E Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 35 of 35
12. base64 encoding Sender Receiver page 29 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 DATAc lt cr gt lt lf gt 354 Enter mail end with on a line by itself Return Receipt To lt module domain com gt lt cr gt lt lf gt Reply To lt module domain com gt lt cr gt lt lf gt From lt module domain com gt lt cr gt lt lf gt To lt receiver Oserver net gt lt cr gt lt lf gt Subject Email test lt cr gt lt lf gt Date Fri 19 Sep 2003 11 41 32 40200 lt cr gt lt lf gt MIME Version 1 0 lt cr gt lt lf gt X Priority 3 Normal lt cr gt lt lf gt X MSMail Priority Normal lt cr gt lt lf gt X Mailer GM862 TELIT SW Build 1 0 1000 1 0 1111 0 lt cr gt lt lf gt Importance Normal lt cr gt lt lf gt X MimeOLE Produced By GM862 TEST SW lt cr gt lt lf gt lt cr gt lt lf gt Content Type text plain lt cr gt lt lf gt charset iso 8859 1 lt cr gt lt lf gt Content Transfer Encoding 7bit lt cr gt lt lf gt lt cr gt lt lf gt This message is sent in order to test Easy GPRS feature Hello World lt cr gt lt lf gt lt cr gt lt lf gt lt cr gt lt lf gt 250 2 0 0 hBJ9QNH3008461 Message accepted for delivery GUIT lt cr gt lt lf gt 221 2 0 0 smtp domain com closing connection d NO CARRIER The Telit module is now back in the command mode 2 3 3 Easy GPRS EMAIL receiving application Let s suppose we want to receive with our
13. bps Flecraauction forbidden without Telit Communications S p A written authorization All Rights Reserved page 10 of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 31 Best Effort e wait for response Response Reason Action OK context parameters have been proceed ahead successfully stored ERROR some error occurred check parameters and retry NOTE If your minimum reguirements are too high then it can happen that it is impossible to establish a GPRS connection because the network has not enough resources to guarantee that quality of service If does this happen then you shall try reducing your minimum quality reguirements For example 1 Let s assume you want to set up the GPRS context number 1 cid written before with your GPRS min OoS parameters Precedence class Normal priority Delay class subscribed Reliability class subscribed Peak throughput not less than 15 6 kbps Mean throughput not less than 7 8 kbps command AT CGQMIN 1 2 0 0 5 4 cr response OK NOTE Telit suggests to setup AT CGQMIN 1 0 0 0 0 0 1 2 3 Requested Quality of the Service The requested quality of service parameters represents the connection quality that is requested to the network on GPRS context activation e send command AT CGQREQ lt cid gt lt precedence gt lt delay gt lt reliability gt lt peak gt lt mean gt lt cr gt where lt cid gt is the index number of the desired
14. ce provider e send command ATD 99 lt cid gt lt cr gt where lt cid gt is the index number of the desired context to be used up to 5 different context e wait for response Response Reason Action CONNECT GPRS connection is being proceed ahead with the processed authentication amp Packed data protocol ERROR some error occurred check context parameters and retry See par 1 2 1 1 2 2 229 check also Network registration status check context parameters and CME ERROR error code gt some error occurred retry See par 1 2 1 1 2 2 Nee check also Network registration status For example 1 Let s assume you want to activate and enter the GPRS state with context number 1 cid written before with your GPRS requested QoS parameters command ATD 99 1 lt cr gt response CONNECT At this point your application should start the PPP protocol with the LCP Exchange phase 2 LCP Configure Request page 13 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 LCP Configure Acknowledge PAP Authentication PAP Ack gt NCP IP Configure Request NCP IP Configure Acknowledge At this point the TCP IP PPP protocol stack is up and data packets can be exchanged NOTE Explanation of TCP IP and PPP protocol stack is beyond the scope of this document Further information on the LCP protocol and PPP protocol definition can be found in the RFC1661 Further informatio
15. der and not the phone number to be dialed therefore it is not possible to establish a direct point to point GPRS connection between two modems as in CSD case instead an internet tunneling must be done to achieve a point to point connection between two peers This approach as the immediate advantage of projecting the controlling application of the GPRS modem directly on the internet ready to be accessed virtually from anywhere in the world at the same cost on the GPRS actually the billing of the GPRS connection is based on the amount of data exchanged number of packets transferred independently from the time the connection is active or where these packet must be delivered Therefore it is possible to leave the controlling application always connected and ready to receive send data on demand while paying only for the data really exchanged The drawback of the GPRS connection is that the controlling application must have its own TCP IP protocol stack embedded to decode the packets that arrive from GPRS and encode the ones to be sent through the internet There are few considerations than must be done on the GPRS connections e the GPRS connection speed with a GPRS class 10 multislot device is asymmetrical 3 time slots in reception 43200 bps max and 2 time slot in sending 28800 bps max or 4 time slots in reception 57600 bps max and 1 time slot in sending 14400 bps max e The controlling application of the module must have a TCP IP PPP softwar
16. e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 e the remote units call the server application modem when needed and eventually retry in the case they found it busy this time the phone number to be stored is only one the server number which must be stored on the remote units In both cases once connected the remote unit sends the meteorological data to the server which places it in a central database for further reading by anyone who accesses the meteorological internet site for example The drawback of this approach is that the CSD modem needs about 30s to establish the connection and depending on the amount of data to be transferred usually few hundreds bytes some seconds to transfer them So let s say we pay a 40s call while we need only 10s to transfer data 1 1 2 GPRS application example The same application can be preformed with all the Telit modules using the GPRS feature The remote unit is always connected to the internet taking advance of the features of the GPRS system when it needs to send data to the server application it simply fills the TCP IP packets for the server with the meteorological data and gives them to the Telit module to deliver The central server has a single modem to connect to the internet receives the TCP IP packets from all the remote units and places the contained data in the central database The advantage of using GPRS is that the remote unit is always connected and reachable and it pay
17. e GPRS context and leaves it active for the page 20 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 future connections until an ATHGPRS 0 command is issued or the network requests a context closing 2 1 3 FTP Client On top of the embedded TCP IP stack an FTP client is available Such FTP is a versatile protocol suite designed to be powerful compact and simple to use for file transfer over the TCP IP and therefore over the GPRS network As far as the AT commands list is concerned the customer shall refer to the AT Commands Reference Guide 2 1 4 Email Client SMTP and POP Application Layer protocol are available on the top of the TCP IP protocol This permits sending and receiving Emails on your embedded device To get more information on system settings and AT commands available for email client please consult the examples in the section 2 2 and AT Commands Reference Guide 2 1 5 Known limitations The implementation of the EASY GPRS feature has the following known limitations e Only one socket can be opened at a time no multiple socket connections can be made e Only one connection reguest can be accepted at a time subseguent reguests will be silently discarded e Only the first GPRS context is associated with this feature It is taken for granted that external processor will be able to handle at least a limited v 24 implementation RTS CTS and highly recommended DOD lines this becau
18. e name string type NOTE The command causes an ERROR result code to be returned if no FTP connection has been opened yet Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 24 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 Example of an FTP file download from the server Define PDP contest AT CGDCONT 1 IP internet wind biz lt cr gt OK GPRS Context Activation as response gives IP of the module ATHGPRS 1 lt cr gt IP 193 199 234 255 OK Opening of FTP connection AT FTPTO 1000 lt cr gt FTP settings of time out OK AT FTPOPEN 199 188 25 77 user pass O lt cr gt OK In this case port of FTP server is not specified which means that it has the default value 21 AT FTPTYPE 0 lt cr gt FTP settings of file type OK AT FTPCWD incoming change working directory if requiered OK In order to get the list of files on the working directory from the server AT command AT FTPLIST should be used Downloading FTP file file txt from the server AT FTPGET file txt lt cr gt CONNECT receive the file Data connection will be closed automatically when the file sending is terminated NO CARRIER AT FTPCLOSE lt cr gt closing FTP connection OK Deactivation of GPRS context if required AT GPRS 0 lt cr gt OK TIP The GPRS command activates the context and it is necessary to start the FTP conn
19. e seen as a way to obtain a virtual serial connection between the Application Software on the Internet machine involved and the controller of the Telit module regardless of all the software stacks underlying An example of the protocol stack involved in the devices is reported Remote Controller Telit Device Device module networks Internet TCP UDP Serial Line Driver network interworking This particular implementation allows to the devices interfacing to the Telit module the use of the GPRS and Internet packet service without the need to have an internal TCP IP stack since this function is embedded inside the module The Easy GPRS overcomes some of the known limitations of the previous implementation and implements some new features such as e Keep the GPRS context active even after the closing of a socket allowing the application to keep the same IP address e Also Mobile terminated incoming connections can be made now it is possible to receive incoming TCP connection requests e A new internal firewall has been implemented in order to guarantee a certain level of security on internet applications IF aS te e Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 16 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 2 1 1 Easy GPRS Outgoing connection The Easy GPRS feature provides a way to place outgoing TCP UDP connections and keep
20. e stack to interface with the GPRS modems A ij Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 5 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 e The controlling application must relay on some ISP that may be the Network Operator of the SIM to gain access to the internet through the GPRS connection e Because of the point before the receiving application must have internet access either e Since the communication is based upon TCP IP packets then it is possible to talk contemporarily with more than one peer e When required the data security in internet shall be guaranteed by security protocols over the TCP IP that must be managed by the controlling application A modem can be in 4 different states e GPRS DETACHED which corresponds to the not reachable condition for the GPRS service e GPRS ATTACHED which corresponds roughly to the registered condition for the GPRS service e GPRS context activated which corresponds to the reachable on the network condition with IP address assigned this is possible with AT command AT GPRS 1 and also some other AT commands e CONNECTED which roughly corresponds to the connected status A thing that must be noted on the GPRS connect is the fact that if the mobile IP address the internet address is assigned by the ISP dynamically then when the GPRS context of the device is not activa
21. ection Reproduction forbidden without Telit Communications S p A written authorization All Rights Ah page 25 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 To get more information for other available commands on the FTP functionality please refer to the AT Commands Reference Guide 2 3 Examples 2 3 1 Easy GPRS HTTP client application Let s suppose we want to connect our embedded device to an HTTP server and retrieve an HTML page using the EASY GPRS feature Initial data Server to be contacted www telit com Application Layer Protocol HTTP1 0 RFC1945 HTTP1 1 RFC2068 Page to be retrieved homepage of server GPRS settings APN internet gprs IP of GPRS device dynamically assigned by the network DNS assigned by the network USERID EASY GPRS PASSWORD EASY GPRS Checking on the RFC990 the HTTP service we can found that the port 80 is dedicated for HTTP service therefore our HTTP server will be waiting for incoming connections on that port and we will fix the EASY GPRS port to be contacted on the remote server exactly to 80 Second thing we have to discover is whether the transport protocol has to be TCP or UDP on the RFC1945 we can read that the HTTP Application layer protocol is meant to be on top of TCP IP protocol therefore the transport protocol choice will fall on TCP Now we have all the information needed to configure our system With our microcontroller we issue to the Teli
22. ee 19 2 1 2 2 Request the socket connection to be opened in listen esses eere 20 2 1 2 5 Receiving connection TEQUEStS 2 1 51 henin ao sab Cha Eo ELE GOLL SEES ban E sao CRUEL ee RARE Fn CDLL 20 PA e olei MI 21 Pm MESS V M 21 2L Known HtA ONS HERE 21 22 FTP OPERATIONS wisecsssssotssscssetesewesstcsivestenessssbeoastbyotesstesncvsiansstousbovbeessubyseecveiyonssavessiensidstosssabeteaaseoveds 22 2 2 1 Opening and Closing an FTP Connection nennen tren nren eren rennen entrent 22 222 Set ngthe FTP Transfer Type ee Re iEn dee clare 23 22 3 FIP File transfer to the Server eee Etui eibi decks i ebbe ie ge 23 224 FIP File download from the server reni nti red b edel eiit ine liie astaat ENSE 24 2 3 Examples 26 2 3 1 Easy GPRS HTTP client application sssini rnense inaire ener nene nennen nennen ne a Ea e nnne 26 2 3 2 Easy GPRS EMAIL sending application eese nennen nennen enne nren enne nr enee nre 28 2 3 3 Easy GPRS EMAIL receiving application eseeeeseeeeeeeeeneennenennnen ennemi nn enne nennen nne noon 30 2 3 4 Remote connection between two modules sees ener nennen nenne nein LL Ynn nnd nn inneren nene 32 Ir rodent OF 4 Document Change LONE
23. eees 8 1 2 1 Context parameter Setting aui au ni si eere eb Pene ect ui e FFIT GM FU GAD 8 1 2 2 Minimum Quality of the Service Requested 00 cceeeeeesssseceseeseeecseesecneeeecsaeeeesaecaeeseesessecsaeeecsaecaeesesaeeaeeaeeneeaes 9 1 2 3 Requested Quality of the Service nde ihe edi ie Eti reip eiTe Ret dees DYM TH FM dnd LY 11 13 GPRS context activation and data state entering cscssccscscscssseccscccseccssccssccesscsssssscssscesscesseeee 13 1 4 GPRS data rio R 15 2 Enhanced Easy GPRS Extension eesseessecesocesooessoesssecssocesocsccocecocessccesocesocessosssseessecssocssosssssesss LO 2 NCF A iiA E YF FY YNOF E E 16 2 1 1 Basy GPRS Outgomg Connection isisisi arean ale a aa deliv Ala 17 2 Ll1 Configure the GPRS access 5s e An de ME E e A a ethos 17 2 1 1 2 Configuring the embedded TCP IP stack eene enne enne nennen 17 2 1 1 3 Saving settings for the Internet peer to be contacted nennen 17 2 1 1 4 Request the GPRS context to be activated eee eeesesecsseesceseceeesecseeeecsaeceesecseesecneeseesaeeeeaesaeeseeneetenaees 18 2 1 1 5 Open the connection with the internet host sese nenne nein etre 18 2 1 1 6 Close the Socket without deactivating the context eene 18 2 1 2 Basy GPRS Incoming Connections cin RO Rec ERE e pg A spese te petu D DEO eta FD ren 19 2 1 2 1 Defining the Internet Peer that can contact this device firewall settings e
24. embedded device an EMAIL by using a POPS server Initial data Server to be contacted POP mail server POP service port 110 Application Layer Protocol POP3 RFC1785 Receiver module lt module domain com gt A Reproduction forbidden without Telit Communications S p A written authorization All Rights Ah page 30 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 Email account username module domain com Email account password telit GPRS settings APN internet gprs IP of GPRS device dynamically assigned by the network DNS assigned by the network USERID EASY GPRS PASSWORD EASY GPRS Checking on the RFC1785 we can found that the port 110 is dedicated for POP3 service therefore our POP server will be waiting for incoming connections on that port and we will fix the EASY GPRS port to be contacted on the remote server exactly to 110 Second thing we have to discover is whether the transport protocol has to be TCP or UDP on the RFC1785 we can read that the POP3 Application layer protocol is meant to be on top of TCP IP protocol therefore the transport protocol choice will fall on TCP Now we have all the information needed to configure our system With our microcontroller we can now issue to the Telit module the following AT commands AT CGDCONT 1 IP internet gprs 0 0 0 0 0 0 lt cr gt 1 GPRS context setting AT USERID EASY GPRS lt cr gt 2 Authentication setting AT PASSWD EASY G
25. ext parameters have been proceed ahead successfully stored ERROR some error occurred check parameters and retry For example 1 Let s assume you want to set up the GPRS context number 1 cid with your GPRS connection parameters APN ibox tim it IP address dynamically assigned by the ISP Packet Data Protocol type Internet Protocol IP Data compression OFF Header compression OFF command AT CGDCONT 1 IP ibox tim it 0 0 0 0 0 0 cr response OK 1 2 2 Minimum Quality of the Service Requested The minimum quality of service requested parameters represent the boundary under which the connection quality is not anymore acceptable and will be terminated e send command AT CGQMIN lt cid gt lt precedence gt lt delay gt lt reliability gt lt peak gt lt mean gt lt cr gt where cid is the index number of the desired context to be written up to 5 different context lt precedence gt is the precedence class It is applied when the network has a heavy duty and user precedence must be followed to ensure operations the higher the priority the better the service 0 subscribed default 1 High priority 2 Normal priority 3 Low priority delay is the delay class It represents the maximum allowable time delay class between the sending and the reception of a packet Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 9 of 35 4 e
26. f max is returned by the Test command PDP type Packet Data Protocol type a string parameter which specifies the type of packet data protocol IP Internet Protocol PPP Point to Point Protocol lt APN gt Access Point Name a string parameter that represents logical name used to select GGSN or external packet data network If the value is null or omitted then the subscription value will be reguested lt PDP_addr gt a string parameter that identifies the terminal in the address space applicable to the PDP The allocated address may be read using the CGPADDR command lt d_comp gt numeric parameter that controls PDP data compression O off default if value is omitted 1 on lt h_comp gt numeric parameter that controls PDP header compression O off default if value is omitted 1 on lt pd1 gt lt pdN gt zero to N string parameters whose meanings are specific to the lt PDP_type gt NOTE a special form of the Set command CGDCONT lt cid gt causes the values for context number lt cid gt to become undefined NOTE issuing AT CGDCONT lt CRs is the same as issuing the Read command NOTE issuing AT CGDCONT lt CRs gt returns the OK result code jo aa Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 8 of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 e wait for response Response Reason Action OK cont
27. hts Reserved page 28 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 For our convenience we will store all these parameters with the command AT SKTSAV lt cr gt Next step is activation of the GPRS context AT GPRS 1 lt cr gt IP 193 199 234 255 OK The command gives as response the IP address assigned by the network Now we can proceed with contacting the server with AT command for socket dial AT SKTD 0 25 smtp domain com 0 0 lt cr gt When we receive the CONNECT indication then we are exchanging data with the SMTP server program on the remote host machine Following the SMTP protocol we proceed with the HELLO presentation and mail delivery directly over the serial line in blu you can find the data sent by us in violet the one received from host 220 smtp domain com ESMTP Service 7 0 027 DD01 ready HELO pcprova lt cr gt lt lf gt 250 smtp domain com AUTH LOGIN lt cr gt lt lf gt 334 VXRIcm8gkXU6 Z204NjJAZG9tYWluLmNvbG lt cr gt lt lf gt 334 UHFzc6dcvmO6 dGVsaXG lt cr gt lt lf gt 235 2 0 0 OK Authenticated MAIL FROM module domain com lt cr gt lt lf gt 250 2 1 0 module domain com Sender ok RCPT TO receiver server net lt cr gt lt lf gt 250 2 1 5 receiver server net Recipient ok Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved authentication method module domain com base64 encoding telit
28. in com Email account password telit Receiver Receiver lt receiver server net gt Subject Email Test Message body This message is sent in order to test Easy GPRS feature Hello World GPRS settings APN internet gprs IP of GPRS device dynamically assigned by the network DNS assigned by the network USERID EASY GPRS PASSWORD EASY GPRS Checking on the RFC990 the SMTP service we can found that the port 25 is dedicated for SMTP service therefore our SMTP server will be waiting for incoming connections on that port and we will fix the EASY GPRS port to be contacted on the remote server exactly to 25 Second thing we have to discover is whether the transport protocol has to be TCP or UDP on the RFC821 we can read that the SMTP Application layer protocol is meant to be on top of TCP IP protocol therefore the transport protocol choice will fall on TCP Now we have all the information needed to configure our system With our microcontroller we issue to the Telit module the following AT commands AT CGDCONT 1 IP internet gprs 0 0 0 0 0 0 lt cr gt 1 GPRS context setting AT USERID EASY GPRS lt cr gt 2 Authentication setting AT PASSW EASY GPRS lt cr gt 2 Authentication setting AT PKTSZ 300 3 Socket setting AT DSTO 50 3 Socket setting AT SKTTO 90 3 Socket setting AT SKTCT 600 ES me 3 Socket setting _ LM Reproduction forbidden without Telit Communications S p A written authorization All Rig
29. n opened yet Example of an FTP file transfer to the server Define PDP contest AT CGDCONT 1 IP internet wind biz lt cr gt OK GPRS Context Activation as response gives IP of the module AT GPRS 1 lt cr gt IP 193 199 234 255 OK Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 23 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 Opening of FTP connection AT FTPTO 1000 lt cr gt FTP settings of time out OK ATEHFTPOPEN lt 199 188 25 77 user pass 0 lt cr gt OK In this case port of FTP server is not specified which means that it has the default value 21 AT FTPTYPE 0 lt cr gt FTP settings of file type OK FTP file transfer to the server in the file named file txt AT FTPPUT file txt lt cr gt CONNECT send the file escape sequence to close the data connection NOCARRIER AT FTPCLOSE lt cr gt closing FTP connection OK Deactivation of GPRS context if required AT GPRS 0 lt cr gt OK 2 2 4 FTP File download from the server With the command AT FTPGET lt filename gt to issued during an FTP connection opens a data connection and starts getting a file lt filename gt from the FTP server If the data connection succeeds a CONNECT indication is sent otherwise a NO CARRIER indication is sent The file is received on the serial port Parameter lt filename gt fil
30. n on the PAP protocol definition can be found in the RFC1334 Further information on the IPCP protocol definition can be found in the RFC1332 O NOTE The CONNECT result code is raised before complete GPRS connection establishment Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 14 of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 1 4 GPRS data state exit 5 LCP Terminate Request LCP Terminate Acknowledge e Wait for NO CARRIER response or in alternative e send escape sequence e wait for 2s default silence time e wait for response Response Reason Action OK Telit module is in command proceed ahead mode now ERROR some error occurred check command syntax and timing and retry NO CARRIER connection has been closed proceed ahead e send command ATH lt cr gt e wait for response Response Reason Action OK GPRS connection has been closed ERROR some error occurred check command syntax and retry 2 Cm Flecraauction forbidden without Telit Communications S p A written authorization All Rights Ah page 15 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 2 Enhanced Easy GPRS Extension 2 1 Overview The Easy GPRS feature allows the Telit module users to contact a device in internet and establish with ita raw data flow over the GPRS and Internet networks This feature can b
31. ng the Internet Peer that can contact this device firewall settings The Telit module has an internal Firewall that controls the behaviour of the incoming connections to the module The firewall applies for INCOMING listening connections OUTGOING connections will be always done regardless of the firewall settings Firewall General policy is DROP therefore all packets that are not included into an ACCEPT chain rule will be silently discarded A a Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 19 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 When packet incomes from the IP address incoming IP the firewall chain rules will be scanned for matching with the following criteria incoming IP amp net mask ip address if the result is yes then the packet is accepted and the rule scan is finished otherwise the next chain is taken into account until the end of the rules when the packet is silently dropped if no matching was found For example let s assume we want to accept connections only from our devices which are on the IP addresses ranging from 197 158 1 1 to 197 158 255 255 We need to add the following chain to the firewall AT FRWL 1 197 158 1 1 255 255 0 0 2 1 2 2 Request the socket connection to be opened in listen With the AT command SKTL socket Listen the TCP request to start listening for connec
32. r the homepage by sending the following lines on the serial line GET HTTP 1 1 lt cr gt lt lf gt Host www telit com lt cr gt lt lf gt Connection keep alive lt cr gt lt lf gt lt cr gt lt lf gt TIP Remember that the strings which are sent to the HTTP server have to be ended by line feed character To see the issued commands enable the local echo As a response to our guery the HTTP server will reply with the HTML code of the homepage and some debugging responses that we will see directly on the serial line HTTP 1 1 200 OK Date Thu 06 2003 10 21 58 GMT Server Apache 1 3 27 Unix Last Modified Thu 06 2003 10 21 58 GMT Content Type text html Connection close lt IDOCTYPE HTML PUBLIC W3C DTD HTML 3 2 FINAL EN gt lt HTML gt here is all the HTML code of the page lt HTML gt lt pause gt lt pause gt Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 27 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 NO CARRIER The Telit module is now back to command mode 2 3 2 Easy GPRS EMAIL sending application Let s suppose we want to send with our embedded device an EMAIL by using a SMTP server Initial data Server to be contacted smtp domain com SMTP service port 25 Application Layer Protocol SMTP RFC821 Sender module lt module domain com gt Email account username module doma
33. s only for the amount of data small transferred and not for the connection time as in CSD operations in addiction the call billing is egual for devices placed anywhere in the Network Operator State and the server can be anywhere in the World Furthermore in the CSD operation the server shall have a set of modems and multiple phone lines to ensure that the calling units will not find it busy while a single modem is enough for GPRS operation The speed at which the packets can be downloaded is up to 57600 bps class 10 device working at 441 4 times faster than CSD In the following paragraphs more detailed information will be given on how to establish GPRS connection page 7 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 1 2 Preliminary GPRS context parameters setting 1 2 1 Context parameter setting The context parameters are all the set of information to identify the internet entry point interface provided by the ISP With these parameters the GPRS network identifies the ISP to be used to gain access to the internet and defines the value of the IP address of the GPRS device once connected e send command AT4CGDCONT lt cid gt lt PDP_type gt lt APN gt lt PDP_ addr gt lt d_comp gt lt h_comp gt lt pd 1 gt LpdN l ll lt cr gt where lt cid gt PDP Context Identifier numeric parameter which specifies a particular PDP context definition 1 max where the value o
34. s limited to 14400 bps An example of this kind of operation is shown in the following picture where the point to point connection is between the two peers as if all the devices inside the dashed line are not present vr P E E d Network interworking h originator tu GSM HSCSD E bb ME Server receiver HSCSD B Flecraauction forbidden without Telit Communications S p A written authorization All Rights Ah page 4 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 In GPRS operations instead the connection is made directly towards internet as if the GPRS modem was a network IP socket interface There s no data path reserved for the data exchange between the two peers instead the resources are allocated dynamically on demand and the data exchanged is organized into packets typically TCP IP furthermore the maximum transfer speed can be much faster than GSM CSD An example of GPRS connection is shown in the following picture where the GPRS connection is between the GPRS modem and the internet as if all the devices inside the dashed line are not present f n D SP mn Public Internet a j SP37 cs l uc Tum t j 2 d intranet GPRS interconnectivity Due to this kind of connection when activating the GPRS connection you must provide the network parameters to enter through the internet point of the GPRS network ISP Internet Service Provi
35. se software flow control is not applicable to the feature Due to the particularity of this feature the flow control of both the directions uplink and downlink is interlocked 5a PEPIS forbidden without Telit Communications S p A written authorization All Rights page of 35 4 e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 2 2 FTP OPERATIONS A set of AT commands is available to support the FTP activities The fist command is called FTPTO FTP Time Out which defines the time out for FTP operations The module has already a factory default time defined that is 10 s If it is needed to be modified the syntax is AT FTPTO lt tout gt Parameter lt tout gt time out in 100 ms units 100 5000 hundreds of ms factory default is 100 NOTE The parameter is not saved in NVM NOTE if parameter lt tout gt is omitted the behaviour of Set command is the same as Read command Example AT FTPTO 1000 lt cr gt set the timeout to 100sec OK 2 2 1 Opening and Closing an FTP Connection With the command AT FTPOPEN lt server port gt lt username gt lt password gt lt mode gt is possible to open the FTP connection The parameters are lt server port gt string type address and port of FTP server factory default port 21 lt username gt string type authentication user identification string for FTP lt passwords string type authentication password for FTP lt mode gt 0
36. t module the following AT commands AT CGDCONT 1 IP internet gprs 0 0 0 0 0 0 lt cr gt 1 GPRS context setting AT USERID EASY GPRS lt cr gt 2 Authentication setting AT PASSW EASY GPRS lt cr gt 2 Authentication setting AT PKTSZ 300 3 Socket setting sets the default packet size to be used by the TCP UDP IP stack for data sending AT DSTO 50 3 Socket setting NOTE For the detailed information about AT commands reported in examples please consult AT Commands Reference Guide e Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 26 of 35 Z e Telit Easy GPRS User Guide 80000ST10028 Rev 0 02 01 07 AT SKTTO 90 3 Socket setting sets the maximum time with no data exchanging on the socket that the module awaits before closing the socket and deactivating the GPRS context AT SKTCT 600 3 Socket setting For our convenience we will store all these parameters with the command AT SKTSAV lt cr gt Next step is activation of the GPRS context AT GPRS 1 lt cr gt IP 193 199 234 255 OK This command replies with the IP address assigned by the network Now we can proceed with contacting the server with AT command for socket dial AT SKTD 0 80 www telit com 0 0 When we receive the CONNECT indication then we are exchanging data with the HTTP server program on the remote host machine Now following the HTTP protocol we ask fo
37. ted it has no address and therefore it cannot be reached by internet requests The same thing occurs in the case the GPRS device has a static IP address assigned to it by the ISP but it is DETACHED In these cases there s no possibility for the internet peer to call the GPRS device through internet the only way to alert it is to call it in GSM mode either a Data or a Voice call are suited and the GPRS module application must recognize the caller eventually abort the GSM call and connect to the internet in GPRS to receive the packets from the internet peer NOTE Mobile device can be reachable from internet network only if the IP assigned by the operator is public IP not all operators offer this service To explain further the differences between CSD and GPRS an example application made in both ways will be shown 1 1 1 CSD application example Let s suppose you have several remote meteorological measurement units spread around the territory and you want to access them wirelessly through a GSM module in CSD operation For each remote unit there s a modem to connect with the server application with its own SIM card and unique phone number Now there are two possibilities e the server application calls on demand the remote units provided it has stored their phone numbers in a private database i n ij Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 6 of 35 Z
38. text which gives as reply the IP of the module assigned by network Now you can open the connection with the remote host with IP address 217 201 142 223 on the port 1024 as in example NOTE IP of the modules can be verified with the following AT command line ATZGPRS 1 Reproduction forbidden without Telit Communications S p A written authorization All Rights Reserved page 33 of 35 3 List of acronyms Abbreviation Description Ack APN AT CM CR CSD CTS DCD FTP GGSN GPRS GSM GTP HTML HTTP HSCSD IP ISDN ISP LCP LLC MS MT Acknowledge Access Point Name Attention commands Command mode Carriage Return Circuit Switched Data Clear To Send Data Carrier Detected File Transfer Protocol Gateway GPRS Serving Support Node General Radio Packet Service Global System for Mobile communication GPRS Tunneling Protocol Hyper Text Markup Language Hypertext Transfer Protocol High Speed Circuit Switched Data Internet Protocol Integrated Services Digital Network Internet Service Provider Link Control Protocol Logical Link Control Mobile Station Mobile Terminated Network Control Protocol Other Equipment Manufacturer Password Authentication Protocol Packet Data Protocol Protocol Data Unit Public Land Mobile Network Point to Point Protocol Quality Of Service Radio Link Control Reduction of Hazardous Substances Ready To Send Subscriber Identity Module Socket Mode Simple Mail Transfer Protocol
39. the same IP address after a connection leaving the GPRS context active The steps reguired to open a socket and close it without closing the GRPS context are configuring the GPRS Access configuring the embedded TCP IP stack behaviour defining the Internet Peer to be contacted reguest the GPRS context to be activated reguest the socket connection to be opened exchange data close the TCP connection while keeping the GPRS active All these steps are achieved through AT commands As for common modem interface two logical statuses are involved command mode and data traffic mode e n Command Mode CM some AT commands are provided to configure the Data Module Internet stack and to start up the data traffic e In data traffic mode Socket Mode SKTM the client can send receive a raw data stream which will be encapsulated in the previously configured TCP IP packets which will be sent to the other side of the network and vice versa Control plane of ongoing socket connection is deployed internally to the module 2 1 1 1 Configuring the GPRS access The GPRS access configuration is done by setting e the GPRS context number 1 parameters see CGDCONT command e the Authentication parameters User Name and Password see commands USERID PASSW 2 1 1 2 Configuring the embedded TCP IP stack The TCP IP stack behaviour must be configured by setting e the packet default size see command PKTSZ e the data sending timeout see command
40. tion requests is executed The Telit module opens a listening socket on the port specified waiting for incoming TCP connections depending on the parameter request with the internet hosts The parameters that shall be specified are the local port where packets shall be received the type of socket and the closing behaviour 2 1 2 3 Receiving connection requests Once the connection request is received the module reports an indication of connection with an unsolicited code CONN FROM lt remote address gt e then connection is accepted and once it is up the module reports the code CONNECT From this moment the data incoming in the serial port is packet and sent to the Internet host while the data received from the host is serialised and flushed to the Terminal Equipment Note that the connections request are FIRST screened in the firewall then if they are accepted they pass to the listening socket therefore only hosts that are in the ACCEPT chain rules of the firewall can induce a connection request the other host requests will be silently discarded without any indication to the remote host for security reasons Once the connection is received and closed the socket is not anymore in listen If the application needs again to be in listen then it shall send again the socket listen SKTL command NOTE before issuing this command the GPRS context should be activated with ATHGPRS 1 When disconnecting the SKTL command does not close th
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