Socket Server crashing after sometime

[Kedar Nath]

Hi,
I have a socket server which has to be running always.
It accepts connections from various clients and creates a thread for each connection to process the data nad save to database.
In each thread created for a connection, the data is read from a buffered input stream and processed.
The program runs well for half a day. There are 2 scenarios observed after some runs.

1) But due to some reason, the server stops listening to requests and there are no data updates in database.
At this point, if i try to simulate a client, the client gets connection refused exception.
On server machine, the server process is still running and processing data for a different client (lets name this as STILLRUNNING_CLIENT).
No new clients are able to connect and once STILLRUNNING_CLIENT disconnects due to network issue, it will also not be able to connect.

2) Server stops running and the process list on the machine does not show socket server process as running.

Please suggest what could be the reasons causing these crashes.