TECHNICAL MANUAL
Telit GM862-GPS
Quad Band GPS Data Terminal Module
Pag.24 of 79
Rev. 0
f) close the socket and GPRS context
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.
3.10.3 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)
3.10.4 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)
3.10.5 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.
3.10.6 Open the connection with the internet host
With the AT#SKTOP all the process required to connect with the internet host starts:
- GM862-GPS
activates
the first context
- GM862-GPS proceeds to the authentication
- Eventually does the DNS query to resolve the IP address of the host name internet
peer
- GM862-GPS establishes a TCP/UDP (depending on the parameter request)
connection with the given internet host
- Once the connection 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.