cotp.h File Reference

TPKT (RFC 1006) + COTP / ISO 8073 X.224 class-0 frame codec (DETWS_ENABLE_COTP) - zero-heap "ISO transport on TCP" framing, the reusable foundation under S7comm and IEC 61850 MMS. More...

#include "ServerConfig.h"

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Detailed Description

TPKT (RFC 1006) + COTP / ISO 8073 X.224 class-0 frame codec (DETWS_ENABLE_COTP) - zero-heap "ISO transport on TCP" framing, the reusable foundation under S7comm and IEC 61850 MMS.

Two stacked layers over TCP:

• TPKT (RFC 1006): a 4-octet envelope - version(1)=3, reserved(1)=0, length(2, big-endian, the whole packet including this header) - then an X.224 TPDU.
• COTP / X.224 class 0: a Data TPDU is LI(1) 0xF0 (EOT|TPDU-NR) then the user data, where LI is the count of header octets after itself. Connection Request / Confirm use codes 0xE0 / 0xD0 and carry a destination ref, a source ref, a class octet, and variable parameters (e.g. the TPDU-size parameter 0xC0).

The builders frame a payload into a caller buffer (fail-closed); the parsers validate and report the slices. TPKT/X.224 layout verified against RFC 1006 / ISO 8073.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file cotp.h.