Rainbow Electronics GT863-PY - Manual (Page 31)

GT863-PY Terminal Product Description
80269ST10026a Rev. 0 - 27/09/06
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page 31 of 50
AT#FRWL=1,"197.158.1.1","255.255.0.0"
3.1.4.2 Request the socket connection to be opened in listen
With the new command #SKTL (socket Listen) the TCP request to start listening for connection
requests is executed:
• GT863-PY 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.
3.1.4.3 Receiving connection requests
Once the connection request is received, the module reports an indication of connection with an
unsolicited code
+CONN FROM: <remote address>
• 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 serialized 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: this command differently from the AT#SKTOP DOES NOT automate all the process of
activating the GPRS, if no GPRS is active the command reports ERROR; therefore before issuing
this command the GPRS shall be activated with AT#GPRS=1 command.
In the same manner, when disconnecting the #SKTL command does not close the GPRS context,
leaving it active for next connections until an AT#GPRS=0 command is issued or the network
requests a context closing.
3.1.5 Known limitations
The implementation of the EASY GPRS feature has the following known limitations:
• Only one socket can be opened at a time, no multiple socket connections can be made;
• Only one connection request can be accepted at a time, subsequent requests will be
silently discarded.