Current language support for protocols

AB-Ethernet reads and offers polled subscriptions in both Java and Go; neither writes.

BACnet/IP (Java) passively receives broadcast traffic and exposes it as subscriptions; it does not read or write properties. The Go driver is the complete one: it reads and writes properties, discovers devices and subscribes to COV notifications.

CAN (raw) (Java) writes and subscribes; there is no read support.

CBus (Java) is a skeleton that connects but implements no operations. The Go driver is the complete one.

ctrlX (Java) answers pings; that is the only operation it completes. Discovery is offered by the driver, but CtrlXPlcDiscoverer.discoverWithHandler is an unimplemented TODO that returns null instead of a future, so a discovery request fails rather than finding anything. Its read, write and subscribe builders are not implemented either, and although the connection carries browse code, browsing does not work yet.

Firmata writes and subscribes in both Java and Go; neither reads. A board is driven and monitored, never polled.

IEC 60870-5-104 subscribes only, in both Java and Go, because the protocol is push driven: the RTU sends unsolicited ASDUs once the session is started, so there is nothing to read or write. The Go driver keeps the IEC quality descriptors alongside each value, so a reading the RTU marked invalid, blocked, substituted or not-topical does not arrive looking like a good one.

KNXnet/IP (C#) is the only driver in plc4net and has not kept pace with the other implementations.

OPC-UA (Go) reads, writes and subscribes over an unencrypted channel, but that is where it ends: only securityPolicy=None actually works, browsing is not implemented, and messages are not chunked, so a request or response larger than a single chunk fails. The Java driver implements the six security policies, browsing and chunking.

Open-Protocol (Java) is a skeleton that connects but implements no operations.

Profinet (Java) discovers devices and browses the submodules of a connected device; neither of the two Java drivers has read or write support. Only the newer profinet-ng driver is part of plc4j-driver-all; the older profinet driver is still in the code base but is not bundled. In profinet-ng a subscription request completes the PROFINET connect handshake, but the subscription response future is deliberately left incomplete and onRegisterConsumer throws UnsupportedOperationException, so no cyclic data ever reaches an application. The unbundled profinet driver does implement that path - it completes the subscription response, registers consumers per subscription handle and dispatches a PlcSubscriptionEvent for every incoming cyclic frame - so the subscribe entry below, which describes what ships, does not apply to it.

SLMP addresses the word devices D, W and R only, in both Java and Go. That is the scope the driver was written to rather than a port gap - the bit devices and the wider MELSEC command set are not implemented in either language.

UMAS (Go) refuses DATE and TIME_OF_DAY tags rather than answering them: the Go data item parser has no case for those field names yet, so the bytes would parse to no value. Every other data type reads and writes. Note also that UMAS ships no test data in any language, so both drivers are verified against each other rather than against a captured exchange.