Communication lines
Lines are the objects of the D2000 system, which defines define parameters of the transfer parameters via physical line (some other systems may call these "channels"). They are defined by logical names and relation to a communication process. In the system, there may be defined several communication lines (real can be defined (although no software limitation is not implemented in D2000, limits in the system may result from the maximum number of threads in the system and the capacity of available memory). For each line defined line in the D2000 system, own a dedicated communication subprocess (thread) is created, that performs independently the communication for . It independently communicates to all Stations belonging to this line. Communication via several lines is performed on individual lines runs in parallel, the communication process is, with regard to communication lines, re-entrant.
Note: for some communication protocols, there may be even multiple threads per-line (e.g. sending/receiving thread for IEC 870-5-104 Client or one-thread-per-client in IEC 870-5-104 Server, or 1-4 threads in Siemens SIMATIC S7 ISO on TCP protocol to support parallel reading).
Object hierarchy - Communication process, Line, Station, I/O Tag
EXT_KOM external communication process is in Starting with D2000 V4.0, the external communication process EXT_KOM is substituted by the KomAPI interface for external communication protocols, that is are implemented as DLL libraries.
...