iOS Question Exception in AsyncStreams_Error on a TCP Socket

[Alessandro71]

After sending some data to an AsyncStream initialized with the streams from a successfully opened TCP Socket, the _Error event sub is called with the following LastException:

<B4IExceptionWrapper: Error Domain=caught_exception Code=0 "*** -streamError only defined for abstract class.  Define -[B4IFastSocket streamError]!" UserInfo={ExceptionName=NSInvalidArgumentException, NSLocalizedDescription=*** -streamError only defined for abstract class.  Define -[B4IFastSocket streamError]!, CallStackSymbols=(
    0   CoreFoundation                      0x00000001996dc2e0 101EB2F1-1915-34A0-8BC9-631D03753B84 + 1135328
    1   libobjc.A.dylib                     0x00000001961a9224 objc_exception_throw + 88
    2   Foundation                          0x0000000197320054 _NSRequestConcreteObject + 0
    3   Foundation                          0x000000019732109c 73841AA3-BFDD-322D-8DC2-E5185A14DEE1 + 11309212
    4   xxx-redacted-app-name                 0x0000000104fb36a0 -[B4IAIN run] + 1440
    5   Foundation                          0x00000001968e6914 73841AA3-BFDD-322D-8DC2-E5185A14DEE1 + 583956
    6   libsystem_pthread.dylib             0x00000001f8f76438 _pthread_start + 136
    7   libsystem_pthread.dylib             0x00000001f8f728cc thread_start + 8
)}>

note that the socket was opened and closed several times and data was sent and received before incurring in the above exception.