> 2.16.5 | Monitoring

> Figure 149: Service and Connection Monitoring
> This section comprises the subsections Description, Used AT Commands and Flow Chart. To move to these subsections please use the Navigation Frame or the appropriate buttons on the toolbar.

> 2.16.5.1 | Description

> Monitoring service is provided in order to enable checking the stability of the connection. The given AT commands are used to request the current states of the service and the connection, which is especially advisible in the polling mode. There are many cases when the states of the connection and service can be changed. The following table shows cases worth monitoring:

> EVENT | SISI (<srvState>) | SICI (<conState>) | Comment
> Open service | 2 → 3 → 4 | 2 | AT^SISO
> PDP context deactivation | → 6 | 0 | Network initiated
> GPRS Detach | → 6 | 0 | Network initiated or AT+CGATT
> GSM Connection temporarily not available | → 4 | 3 | +CREG: 2
> End of data | 4 → 5 → 6 or 4 → 6 | 2 | <eodFlag>=1
> TcpOT/TcpMR expires | → 6 | 2 |
> Close Service before inactivity timer has timed out | → 2 | 2 | AT^SISC
> Close Service after inactivity timer has timed out | → 2 | 0 | AT^SISC

> • | Note that Socket Listener service remains in the state “3” (Connecting) during the whole session and the SMTP service proceeds to the state “4” (Up) after first write transfer with the AT^SISW command.

> • | There is also possibility of the hardware monitoring. If the AT&C is set to 2, DCD line will be ON during some states of the different services. (for exact description see [2]).

> 2.16.5.2 | Used AT commands

> Command | Explanation
> AT^SISI | Internet Service Information
> AT^SICI | Internet Connection Information
> AT^SISE | Internet Service Error Report

> For further details about the commands see [2].

> 2.16.5.3 | Flow chart

> Figure 150: Service and Connection Monitoring.