Phase 3 PR 43 — followup commit: validate pymodbus simulator end-to-end + fix three real bugs surfaced by running it. winget-installed Python 3.12.10 + pip-installed pymodbus[simulator]==3.13.0 on the dev box; both profiles boot cleanly, the integration-suite smoke test passes against either profile.

Three substantive issues caught + fixed during the validation pass:
1. pymodbus rejects unknown keys at device-list / setup level. My PR 43 commit had `_layout_note`, `_uint16_layout`, `_bits_layout`, `_write_note` device-level JSON-comment fields that crashed pymodbus startup with `INVALID key in setup`. Removed all device-level _* fields. Inline `_quirk` keys WITHIN individual register entries are tolerated by pymodbus 3.13.0 — kept those in dl205.json since they document the byte math per quirk and the README + git history aren't enough context for a hand-author reading raw integer values. Documented the constraint in the top-level _comment of each profile.
2. pymodbus rejects sweeping `write` ranges that include any cell not assigned a type. My initial standard.json had `write: [[0, 2047]]` but only seeded HR[0..31] + HR[100] + HR[200..209] + bits[1024..1109] — pymodbus blew up on cell 32 (gap between HR[31] and HR[100]). Fixed by listing per-block write ranges that exactly mirror the seeded ranges. Same fix in dl205.json (was `[[0, 16383]]`).
3. pymodbus simulator stores all 4 standard Modbus tables in ONE underlying cell array — each cell can only be typed once (BITS or UINT16, not both). My initial standard.json had `bits[0..31]` AND `uint16[0..31]` overlapping at the same addresses; pymodbus crashed with `ERROR "uint16" <Cell> used`. Fixed by relocating coils to address 1024+, well clear of the uint16 entries at 0..209. Documented the layout constraint in the standard.json top-level _comment.
Substantive driver bug fixed: ModbusTcpTransport.ConnectAsync was using `new TcpClient()` (default constructor — dual-stack, IPv6 first) then `ConnectAsync(host, port)` with the user's hostname. .NET's TcpClient default-resolves "localhost" to ::1 first, fails to connect to pymodbus (which binds 0.0.0.0 IPv4-only), and only then retries IPv4 — the failure surfaces as the entire ConnectAsync timeout (2s by default) before the IPv4 attempt even starts. PR 30's smoke test silently SKIPPED because the fixture's TCP probe hit the same dual-stack ordering and timed out. Both fixed: ModbusSimulatorFixture probe now resolves Dns.GetHostAddresses, prefers AddressFamily.InterNetwork, dials IPv4 explicitly. ModbusTcpTransport does the same — resolves first, prefers IPv4, falls back to whatever Dns returns (handles IPv6-only hosts in the future). This is a real production-readiness fix because most Modbus PLCs are IPv4-only — a generic dual-stack TcpClient would burn the entire connect timeout against any IPv4-only PLC, masquerading as a connection failure when the PLC is actually fine.
Smoke-test address shifted HR[100] -> HR[200]. Standard.json's HR[100] is the auto-incrementing register that drives subscribe-and-receive tests, so write-then-read against it would race the increment. HR[200] is the first cell of a writable scratch range present in BOTH simulator profiles. DL205Profile.cs xml-doc updated to explain the shift; tag name "DL205_Smoke_HReg100" -> "Smoke_HReg200" + smoke test references updated. dl205.json gains a matching scratch HR[200..209] range so the smoke test runs identically against either profile.
Validation matrix:
- standard.json boot: clean (TCP 5020 listening within ~3s of pymodbus.simulator launch).
- dl205.json boot: clean.
- pymodbus client direct FC06 to HR[200]=1234 + FC03 read: round-trip OK.
- raw-bytes PowerShell TcpClient FC06 + 12-byte response: matches FC06 spec (echo of address + value).
- DL205SmokeTest against standard.json: 1/1 pass (was failing as 'BadInternalError' due to the dual-stack timeout + tag-name typo — both fixed).
- DL205SmokeTest against dl205.json: 1/1 pass.
- Modbus.Tests Unit suite: 52/52 pass — dual-stack transport fix is non-breaking.
- Solution build clean.
Memory + future-PR setup: pymodbus install + activation pattern is now bullet-pointed at the top of Pymodbus/README.md so future PRs (the per-quirk DL205_<behavior> tests in PR 44+) don't have to repeat the trial-and-error of getting the simulator + integration tests cooperating. The three bugs above are documented inline in the JSON profiles + ModbusTcpTransport so they don't bite again.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-04-18 21:14:02 -04:00
parent a05b84858d
commit 02fccbc762
6 changed files with 110 additions and 50 deletions

View File

@@ -1,5 +1,5 @@
{
"_comment": "DL205.json — AutomationDirect DirectLOGIC DL205/DL260 quirk simulator. Models each behavior in docs/v2/dl205.md as concrete register values so DL205_<behavior> integration tests can assert against this profile WITHOUT a live PLC. Loaded by `pymodbus.simulator`. See ../README.md. Per-quirk address layout matches the table in dl205.md exactly. `shared blocks: true` matches DL series behavior — coils/HR overlay the same word address space (a Y-output is both a discrete bit AND part of a system V-memory register).",
"_comment": "DL205.json — DirectLOGIC DL205/DL260 quirk simulator. Models docs/v2/dl205.md as concrete register values. NOTE: pymodbus rejects unknown keys at device-list / setup level; explanatory comments live at top-level _comment + in README + git. Inline _quirk keys WITHIN individual register entries are accepted by pymodbus 3.13.0 (it only validates addr / value / action / parameters per entry). Each quirky uint16 is a pre-computed raw 16-bit value; pymodbus serves it verbatim. shared blocks=true matches DL series memory model. write list mirrors each seeded block — pymodbus rejects sweeping write ranges that include undefined cells.",
"server_list": {
"srv": {
@@ -27,15 +27,37 @@
},
"invalid": [],
"write": [
[0, 16383]
[0, 0],
[200, 209],
[1024, 1024],
[1040, 1042],
[1056, 1057],
[1072, 1072],
[1280, 1282],
[1343, 1343],
[1407, 1407],
[2048, 2050],
[3072, 3074],
[4000, 4007],
[8448, 8448]
],
"_comment_uint16": "Holding-register seeds. Every quirky value is a raw uint16 with the byte math worked out in dl205.md so the simulator serves it verbatim — pymodbus does NOT decode strings, BCD, or float-CDAB on its own; that's the driver's job.",
"uint16": [
{"_quirk": "V0 marker. HR[0] = 0xCAFE proves register 0 is valid on DL205/DL260 (rejects-register-0 was a DL05/DL06 relative-mode artefact). 0xCAFE = 51966.",
{"_quirk": "V0 marker. HR[0]=0xCAFE proves register 0 is valid on DL205/DL260 (rejects-register-0 was a DL05/DL06 relative-mode artefact). 0xCAFE = 51966.",
"addr": 0, "value": 51966},
{"_quirk": "Scratch HR range 200..209 — mirrors the standard.json scratch range so the smoke test (DL205Profile.SmokeHoldingRegister=200) round-trips identically against either profile.",
"addr": 200, "value": 0},
{"addr": 201, "value": 0},
{"addr": 202, "value": 0},
{"addr": 203, "value": 0},
{"addr": 204, "value": 0},
{"addr": 205, "value": 0},
{"addr": 206, "value": 0},
{"addr": 207, "value": 0},
{"addr": 208, "value": 0},
{"addr": 209, "value": 0},
{"_quirk": "V2000 marker. V2000 octal = decimal 1024 = PDU 0x0400. Marker 0x2000 = 8192.",
"addr": 1024, "value": 8192},
@@ -57,16 +79,14 @@
{"_quirk": "BCD register. Decimal 1234 stored as BCD nibbles 0x1234 = 4660. NOT binary 1234 (= 0x04D2).",
"addr": 1072, "value": 4660},
{"_quirk": "FC03 cap test. Real DL205/DL260 FC03 caps at 128 registers (above spec's 125). HR[1280..1407] is 128 contiguous registers; rest of block defaults to 0.",
{"_quirk": "FC03 cap test marker — first cell of a 128-register span the FC03 cap test reads. Other cells in the span aren't seeded explicitly, so reads of HR[1283..1342] / 1344..1406 return the default 0; the seeded markers at 1280, 1281, 1282, 1343, 1407 prove the span boundaries.",
"addr": 1280, "value": 0},
{"addr": 1281, "value": 1},
{"addr": 1282, "value": 2},
{"addr": 1343, "value": 63, "_marker": "FC03Block_mid"},
{"addr": 1407, "value": 127, "_marker": "FC03Block_last"}
{"addr": 1343, "value": 63},
{"addr": 1407, "value": 127}
],
"_comment_bits": "Coils — Y outputs at 2048+, C relays at 3072+, scratch C at 4000-4007 for write tests. DL260 X inputs would be at discrete-input addresses 0..511 but pymodbus's shared-blocks mode + same-table-as-coils means those would conflict with HR seeds; FC02 tests against this profile use a separate discrete-input block instead — that's why `di size` is large but the X-input markers live in `bits` only when `shared blocks=false`. Document trade-off in README.",
"bits": [
{"_quirk": "Y0 marker. DL260 maps Y0 to coil 2048 (0-based). Coil 2048 = ON proves the mapping.",
"addr": 2048, "value": 1},