Rainbow Electronics GM862-QUAD-PY - Manual (Page 27)

Easy GPRS User Guide
80000ST10028 Rev. 4 - 16/07/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 27 of 63
When packet incomes from the IP address <incoming IP>, the firewall chain rules will be scanned for
matching with the following criteria:
<incoming IP> & <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
The new listen command is now extended to 6 connections, it’s possible to set from 1 to 6 socket
listening on a specific port for the incoming connections. Another difference with the old IP Easy is that
now we receive an unsolicited indication when someone tries to connect, so we can decide to accept
(AT#SA) or refuse (AT#SH) the incoming connection.
NOTE: In case you decide to reject an incoming connection request the listening socket will be closed
and if you want to re-open it the AT command AT#SL needs to be re-issued.
The command syntax is:
AT#SL = <Conn Id>, <Listen state>, <Listen port>[, <Closure Type>]
It’s not possible to have two ConnId listening on the same port.
Example:
Suppose that we want to listen on port 6543 Connection Id number 2
AT#SL = 2, 1, 6543
OK
Now the module is listening for incoming connection on port 6543 with Connection Id number 2, if a
remote host is trying to connect we’ll receive a SRING unsolicited indication with the listening
Connection Id:
SRING: 2