User's Manual

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TECHNICAL MANUAL
Telit GM862 PCS
Tri Band GPRS Data Terminal System Rev.1
All these steps are achieved through AT commands.
As for common modem interface, two logical status are involved: command mode and data traffic
mode.
- In Command Mode (CM), some AT commands are provided to configure the Data Module
Internet stack and to start up the data traffic.
- 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 viceversa. Control plane of ongoing socket connection is
deployed internally to the module.
2.9.2.1 Configuring the GPRS access
The GPRS access configuration is done by setting:
- the GPRS context number 1 parameters (see +CGDCONT command)
- the Authentication parameters: User Name and Password (see commands #USERID, #PASSW)
2.9.2.2 Configuring the embedded TCP/IP stack
The TCP/IP stack behaviour must be configured by setting:
- the packetizer default packet size (see command #PKTSZ)
- the data sending timeout (see command #DSTO)
- the socket inactivity timeout (see command #SKTTO)
2.9.2.3 Defining the Internet peer to be contacted
As last setting definition, the host to be contacted and on which port/protocol must be set :
- the socket definition (see command #SKTSET)
This command permits also to specify the host name instead of its IP address, if a host name is
given to the set command, then the module stores it as a host nick name. It is care of the module
user to guarantee that the host nick name provided corresponds to an existing internet peer.
If an host nick name has been given then, while opening the connection in response to the
AT#SKTOP command, the module will autonomously activate a GPRS connection and query its
DNS to obtain the IP address relative to the host nick name provided. This process of context
activation and DNS query may require a bit more time and requires that the GPRS network
coverage is good enough to permit data transfers.
2.9.2.4 Open the connection with the internet host
With the AT#SKTOP all the process required to connect with the internet host starts:
- GM862-PCS activates the first context
- GM862-PCS proceeds to the authentication with the parameters specified on par. 2.9.2.1
- Eventually does the DNS query to resolve the IP address of the host name internet peer