I test the connection in both directions, i.e. SIM908->SocketTest & SocketTest-> SIM908, and both worked successfully. After some time, approx. 10minutes, the connection stalls, and whenever I try to send data (both ways), no data is sent/received succesfully.
When I check the status of the SIM908 (using AT+CIPSTATUS), it first says "CONNECT OK". Then SocketTest says "Server closed Client connection". If I then check again the SIM908, it says "TCP CLOSED".
It seems as if, the connection stops automatically after some time. I have gone through the AT command manual of the SIM908, but there doesn't seem to be any such option.