sim_tcp_send fails in case of GPRS network disconnection

[mohamedboubaker]

The sim_tcp_send function below to send the TCP payload without checking if the underlying GPRS connection is still on. When the GPRS connection is disconnected, sim_tcp_send will fail with unpredictable behavior.

Note: GPRS connection could disconnected for several reasons:
a cell handover could go wrong
the network could disconnect the device
the cell is not reachable

[mohamedboubaker]

To attempt to solve the issue, we need a function to check the GPRS status, and then depending on the Status we need to try to reconnect

• create a function to check the status of the GPRS network #27