Communication errors are identified by the file names: ServerConnection.cpp and ServerTransportTCPSSL.cpp.
They usually occur when the sensor has a problem communicating with the server. The problem might be transient (such as a network disconnect). It is best to examine the log to see if the communication resumed following the error.
An error log entry (followed by warning message with more info) indicating failure to communicate:
Mon Aug 26 2013 03:50:40.258 T[2072] F[ServerConnection.cpp] L[249] ERROR Failed to send message now
Mon Aug 26 2013 03:51:10.259 T[2072] F[ServerTransportTCPSSL.cpp] L[530] WARNING Unable to connect to server xx.xx.xx.xx(host.com):1996 (Resource temporarily unavailable) randStatus(1), errno is 10035, ssl err: error:00000000:lib(0):func(0):reason(0)
Log line later upon successful connection:
Mon Aug 26 2013 03:51:20.480 T[2072] F[ServerTransportTCPSSL.cpp] L[609] NOTICE Connected to server: xx.xx.xx.xx local IP: xx.xx.xx.xx(host.com)