The link procedures are described in the standard IEC 60870-5-104/Part 5-104: Transmission protocols – Network access for IEC 60870-5-101 using standard transport profiles, IEC 60870-5-104 interoperability.
Note: If the IEC 60870-5-104 client disappears, the established TCP/IP socket connection is closed by the relay or server. This occurs either as a TCP socket keep-alive failure or as time-outs t1 and t2, whichever happens first.