Gotchas
Use this page only for library-specific caveats.
Use the shared KV Host Link Troubleshooting & Codes page for common connection, profile, address-shape, write-permission, and PLC error-code symptoms.
Current library-specific caveats
| Area | Symptom | Guidance |
|---|---|---|
| Network | An IPv6 literal or IPv6-only host fails before socket creation. | Use an IPv4 address or a host name with an IPv4 DNS result; this library intentionally does not support IPv6. |
| RDC comments | A :COMMENT read fails before connect, or malformed bytes close the supplying connection. |
Select text plus exact utf8/cp932, or select raw buffer. The library never guesses or falls back; cp932 is Windows-31J/KEYENCE Shift_JIS compatibility. |
| Compound reads | A large readNamed can observe values from different PLC instants. |
Splitting is read-only and non-atomic. Use one request or a PLC-side consistency handshake when coherence matters. |
| Writes | Numeric/string bit values or implicit bit-in-word named writes are rejected. | Supply JavaScript Booleans for direct-bit writes. Call writeBitInWord or writeBitInExpansionUnitBuffer explicitly only when their two-request, non-PLC-atomic semantics and lost-update risk are acceptable. |
| Outcome unknown | A timeout/cancel/close/invalid response after a write yields HostLinkOperationOutcomeUnknownError. |
Do not retry automatically; reconcile state, reconnect explicitly, then decide. |