The IEC 60870-5-104 protocol handler is located in the IEC60870 Wrapper Feature.
To use the IEC60870 Wrapper Feature, one has to install the j60870 Feature that is licensed under the GPLv3. The j60870 Feature contains the j60870 library that is originally developed by Stefan Feuerhahn (Frauenhofer ISE) and provided by openMUC under the GPLv3. It is modified by the University of Oldenburg.
The protocol itself
See IEC 60870-5-104 Transport handler for a description of the protocol.
IEC 60870-5-104 protocol handler
This is a simplified version that does not implement the handshake etc. It just converts a byte array into an ASDU. This protocol handler is useful for interpret Pcap files that contain IEC 60870-5-104 messages. For an example, see Pcap file transport handler.