Reaches the first major milestone of Phase 4: acdream's codec is proven
byte-compatible with a live ACE server. LiveHandshakeTests drives a real
UDP exchange against 127.0.0.1:9000 and successfully negotiates the
first half of the connect handshake.
Added:
- Packets/PacketHeaderOptional.cs: new ConnectRequest flag branch.
ACE's AGPL parser doesn't decode ConnectRequest (server only sends
it) so this is new client-side code. Exposes ConnectRequestServerTime,
Cookie, ClientId, ServerSeed, ClientSeed — the values we need to
seed our two ISAAC instances and echo the cookie back in a
ConnectResponse.
- NetClient.cs: minimum-viable UDP transport, a thin UdpClient wrapper
with synchronous Send and timeout-based Receive. No background thread
or retransmit window yet — good enough for handshake bring-up and
the offline state-machine tests.
- LiveHandshakeTests.cs: gated behind ACDREAM_LIVE=1 environment
variable so CI without a server doesn't fail. Reads credentials
from ACDREAM_TEST_USER / ACDREAM_TEST_PASS (never logged or
committed), builds a LoginRequest datagram via our codec, sends
it to localhost:9000, waits for up to 5s for a response, and
asserts we receive a ConnectRequest with non-zero cookie, clientId,
and both ISAAC seeds.
Tests (5 new, 77 total in net project, 154 across both projects):
- ConnectRequestTests: two offline tests exercising the new
PacketHeaderOptional branch via synthetic datagrams. One verifies
every field round-trips through Encode + TryDecode, one feeds the
extracted 32-bit seeds into IsaacRandom to prove they work as
keystream seeds.
- NetClientTests: 2 offline tests — loopback SendReceive round-trip
between two NetClient instances (proves UDP pump is alive without
needing any server), and Receive-with-timeout returning null
cleanly when no datagram arrives.
- LiveHandshakeTests: 1 live integration test (early-exits when
ACDREAM_LIVE env var not set, so it passes trivially in CI).
LIVE RUN OUTPUT (against user's localhost ACE server):
[live] sending 84-byte LoginRequest to 127.0.0.1:9000 (user.len=11, pass.len=12)
[live] received 52-byte datagram from 127.0.0.1:9000
[live] decode result: None, flags: ConnectRequest
[live] ConnectRequest decoded: serverTime=290029541.121 cookie=0xAC45998D06754133
clientId=0x00000001 serverSeed=0x4CC09763 clientSeed=0x5C3DE13E
Meaning: 84-byte LoginRequest went out, 52-byte ConnectRequest came
back, codec.TryDecode returned None error, every field parsed to a
sensible value. This proves byte-compatibility of both directions at
the protocol layer, ISAAC seed extraction path, Hash32 checksum on
both encode and decode, and the whole String16L/String32L/bodyLength
layout of LoginRequest against the real server parser.
Next step: send ConnectResponse echoing the cookie so the server
promotes us to "connected" and starts streaming CharacterList +
CreateObject messages (those will use EncryptedChecksum, which is
where our ISAAC implementation gets its ultimate test).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Completes the encode side of the codec so acdream can stop hand-
assembling outbound packets in tests. Given a PacketHeader (with Flags
set, DataSize ignored/overwritten) and a body byte span, Encode:
1. Overwrites header.DataSize with body.Length
2. Parses the optional section out of the body (reusing
PacketHeaderOptional.Parse as a length measurer) and hashes those bytes
3. If BlobFragments is set, walks the body tail as back-to-back
fragments and sums their Hash32s
4. For unencrypted: header.Checksum = headerHash + optionalHash + fragmentHash
5. For EncryptedChecksum: pulls one ISAAC keystream word and computes
header.Checksum = headerHash + (isaacKey XOR payloadHash)
6. Packs header + body into the final datagram
Tests (6 new, 67 total in net project, 144 across both test projects):
- Unencrypted round-trip: Encode then TryDecode recovers the AckSequence
field
- DataSize is overwritten (caller can pass garbage)
- Encrypted round-trip: two ISAACs with same seed, one encoding and
one decoding, both agree on the keystream word
- Encrypted but no ISAAC → throws InvalidOperationException
- LoginRequest end-to-end: LoginRequest.Build → Encode → TryDecode →
LoginRequest.Parse round-trips credentials exactly. This is the
single most important integration test for the outbound side —
every byte this exercises is exactly what acdream will put on the
wire when Phase 4.6 goes live.
- BlobFragments body with one embedded fragment: Encode preserves
the fragment and fragmentHash is correctly folded into the checksum
Codec is now complete end-to-end (decode + encode) and has the
LoginRequest outbound path proven against its own decoder. The next
commit will wire NetClient over real UDP sockets and connect to the
localhost ACE server.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds the outbound-side primitives acdream needs to send a LoginRequest
packet to an ACE server: a growable byte buffer writer with AC's two
length-prefixed string formats, plus the LoginRequest payload builder
and parser.
PacketWriter (Packets/PacketWriter.cs):
- Growable byte[] buffer with little-endian WriteByte/UInt16/UInt32/Bytes
- WriteString16L: u16 length + ASCII bytes + zero-pad to 4-byte boundary
(pad counted from start of length prefix, matching ACE's Extensions.cs)
- WriteString32L: u32 outer length (= asciiLen+1) + 1 marker byte (value
ignored by reader, we emit 0) + ASCII + pad. Reader decrements the
outer length by 1 when consuming the marker, so asciiLen is recovered
correctly. Asserts ≤255 chars (two-byte-marker variant not needed for
acdream's dev credentials).
- ASCII encoding used instead of Windows-1252 since dev account names
and passwords are ASCII-safe; can switch to CodePages later if a
non-ASCII identifier ever turns up.
LoginRequest (Packets/LoginRequest.cs):
- Build(account, password, timestamp, clientVersion="1802") produces
the login payload bytes that go into the body of a packet whose
header has the LoginRequest flag set
- Parse(bytes) for tests and diagnostics — server never calls this
in production, but round-trip tests make the writer self-verifying
- NetAuthType enum mirrors ACE: Account/AccountPassword/GlsTicket
- Wire layout per ACE's PacketInboundLoginRequest:
String16L ClientVersion
u32 bodyLength (bytes remaining after this field)
u32 NetAuthType (2 = AccountPassword)
u32 AuthFlags (0 for normal client)
u32 Timestamp
String16L Account
String16L LoginAs (empty for non-admin)
String32L Password (when AccountPassword)
- bodyLength field is back-patched after the full body has been
written (classic "write placeholder, come back and patch" flow)
Tests (17 new, 61 total in net project, 138 across both test projects):
PacketWriter (11):
- u32 little-endian
- String16L: empty, 1/2/3-char with correct padding
- String32L: 2-char short, empty, >255 throws
- AlignTo4 no-op when aligned, pads when not
- Buffer grows past initial capacity on big writes
LoginRequest (6):
- Build→Parse round-trip with realistic credentials (testaccount/
testpassword/timestamp)
- Empty account/password round-trip (padding edge case)
- BodyLength field reflects actual remaining bytes after itself
- Total wire size is multiple of 4 (sanity check on padding)
- Different credentials produce different bytes
- End-to-end: payload embedded in a full Packet with LoginRequest
header flag + correct unencrypted checksum, PacketCodec.TryDecode
parses it, BodyBytes round-trips back to the same credentials
through LoginRequest.Parse
This gives acdream everything needed to construct the first datagram
of the handshake. Phase 4.5c next: WorldSession state machine to drive
the handshake sequence.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Brings the codec to end-to-end: a raw UDP datagram goes in, a parsed
Packet comes out with verified CRC (both plain and ISAAC-encrypted
variants). Synthetic packets built inside tests round-trip through
TryDecode cleanly.
Added:
- Packets/PacketHeaderOptional.cs: parses every flag-gated section
that lives between the 20-byte header and the body fragments —
AckSequence, RequestRetransmit (with count + array), RejectRetransmit,
ServerSwitch, LoginRequest (tail slurp), WorldLoginRequest,
ConnectResponse, CICMDCommand, TimeSync (double), EchoRequest (float),
Flow (FlowBytes + FlowInterval). Records the raw consumed bytes into
RawBytes so CalculateHash32 can hash them verbatim — AC's CRC requires
hashing the optional section separately from the main header and the
fragments.
- Packets/Packet.cs: a record type bundling Header, Optional, Fragments,
and the raw body bytes. Produced by the decoder, consumed by downstream
handlers in Phase 4.5.
- Packets/PacketCodec.cs: TryDecode(datagram, isaac?) that
1. Unpacks the header,
2. Bounds-checks DataSize against the buffer,
3. Parses the optional section,
4. If BlobFragments is set, walks the body tail as back-to-back
MessageFragment.TryParse calls,
5. Computes headerHash + optionalHash + fragmentHash,
6. Verifies CRC:
- Unencrypted: sum equals header.Checksum
- Encrypted: (header.Checksum - headerHash) XOR payloadHash must
equal the next ISAAC keystream word (which is consumed on match)
Returns a PacketDecodeResult(Packet?, DecodeError) so callers can log
and drop malformed packets instead of throwing.
- Public helper PacketCodec.CalculateFragmentHash32 so tests (and later
the encode path) can reuse the fragment-hash math.
Tests (7 new, 44 total in net project, 121 across both test projects):
- Minimal valid packet with AckSequence optional, no fragments, plain
checksum — verifies optional parse + CRC accept
- Wrong checksum rejected
- Buffer shorter than header → TooShort
- Header DataSize > buffer → HeaderSizeExceedsBuffer
- Packet with BlobFragments flag + one fragment: parses fragment and
validates the full headerHash + fragmentHash equals wire checksum
- Encrypted checksum ROUND TRIP: two ISAAC instances with same seed,
one encodes the checksum key, one decodes — validates the
(Header.Checksum - headerHash) XOR payloadHash == isaacNext contract
byte-for-byte
- Encrypted checksum with wrong key on the wire → rejected
Known limitation: the parser advances past WorldLoginRequest and
ConnectResponse their full 8 bytes whereas ACE "peeks" them (seek/reset).
The on-wire byte count is the same, only the read-position behavior
differs; any consumer that wanted to re-read those sections can do so
from Packet.BodyBytes.
Phase 4.5 (NetClient UDP pump + handshake state machine) next.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Ports the fragment layer of the AC UDP protocol. A UDP packet's body is
zero or more message fragments back-to-back; a logical GameMessage that
doesn't fit in ~448 bytes gets split across multiple fragments sharing
the same Id with differing Index values. The assembler handles
reassembly across arbitrary arrival ordering and duplicate fragments.
Added (all reimplemented from ACE's AGPL reference, see NOTICE.md):
- Packets/MessageFragmentHeader.cs: 16-byte fragment header struct
with Pack/Unpack, constants for MaxFragmentSize (464) and
MaxFragmentDataSize (448). Bit-layout doc comment documents what
each field is for.
- Packets/MessageFragment.cs: readonly record struct bundling a
header with its payload bytes; TryParse(source) parses one fragment
from the start of a buffer and returns (fragment, consumed) for
incremental parsing of multi-fragment packets. Refuses to parse
fragments with impossible TotalSize (too small for header, too
large for the 464-byte max, or larger than the source buffer).
- Packets/FragmentAssembler.cs: buffers partial messages keyed by
fragment Id. Ingest(frag, out queue) returns the assembled byte[]
when the last fragment arrives, null while still waiting. Key
correctness properties, all tested:
* Single-fragment (Count=1) shortcut releases with no buffering
* Out-of-order arrival (e.g. 2, 0, 1) releases on last arrival
and assembles in INDEX order, not arrival order
* Duplicate-fragment idempotence (re-sending same index is a no-op)
* Missing fragments stay buffered; DropAll() forcibly clears them
* Two independent messages can be assembled in parallel without
interfering
* messageQueue captured from first-arriving fragment (it's a
property of the logical message, not individual fragments)
Tests (17 new, 37 total in net project, 114 across both test projects):
- MessageFragmentHeader (4): pack/unpack round-trip, little-endian
wire format, constants, size-check throw
- MessageFragment (6): complete parse, insufficient header, oversized
TotalSize, undersized TotalSize, incomplete body, two-back-to-back
incremental parse
- FragmentAssembler (7): single-fragment, in-order 3-fragment,
out-of-order 3-fragment (tests index-order assembly), duplicate
idempotence, missing-fragment buffered, two parallel messages,
DropAll
Phase 4.4 (GameMessage reader + opcode handlers) next.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Adds the 20-byte AC UDP packet header struct + pack/unpack + its
checksum helper, and the Hash32 primitive the checksum uses.
Hash32 (Cryptography/Hash32.cs):
- Seeds accumulator with length << 16
- Sums input as little-endian uint32s word-aligned
- Folds any trailing 1-3 bytes via descending shift (24 → 16 → 8)
- Hand-computed golden values for 4-byte, 5-byte, and each 1/2/3
tail-byte case — no oracle needed, algorithm is simple enough to
verify by tracing
PacketHeader (Packets/PacketHeader.cs):
- Pack/Unpack: Sequence, Flags, Checksum, Id, Time, DataSize, Iteration
(20 bytes, little-endian on the wire)
- CalculateHeaderHash32: substitutes the 0xBADD70DD sentinel for the
Checksum field before hashing (matches AC retail + ACE convention —
without it the checksum would chicken-and-egg on itself). Uses a
local struct copy so the real Checksum isn't mutated on the caller.
- HasFlag for bitmask queries
PacketHeaderFlags (Packets/PacketHeaderFlags.cs):
- Full flag enum from ACE reference: Retransmission, EncryptedChecksum,
BlobFragments, ServerSwitch, ConnectRequest/Response, LoginRequest,
AckSequence, TimeSync, Disconnect, NetError, EchoRequest/Response,
Flow, and friends
Tests (15 new, 20 total in net project, 97 across both projects):
Hash32 (7):
- Empty returns 0
- 4-byte known value (hand-computed from bit layout)
- 5-byte value with one tail byte
- 1/2/3 tail-byte boundary cases (verifies 24/16/8 shift ordering)
- Determinism
PacketHeader (8):
- Pack/Unpack round-trip preserving all 7 fields
- Pack writes little-endian wire format in byte order
- HasFlag single and multi-bit
- CalculateHeaderHash32 invariance under Checksum field changes
(the critical property — verifies the BADD sentinel substitution)
- CalculateHeaderHash32 doesn't mutate
- CalculateHeaderHash32 determinism
- Unpack/Pack size-check throw
User confirmed an ACE server is running on localhost for the future
Phase 4.6 live integration step. Credentials will be read from env
vars at runtime, never committed.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
First step of Phase 4 (networking). Adds a new AcDream.Core.Net project
for the AC UDP protocol implementation and a matching AcDream.Core.Net.Tests
project. Keeps networking isolated from rendering and the dat layer,
which also keeps the AGPL-reference-material hygiene cleaner.
AcDream.Core.Net/NOTICE.md documents the attribution policy: we read
ACE's AGPL network code (and holtburger's Rust ac-protocol crate) to
understand AC's wire format, but we reimplement everything in acdream's
own style. Wire-format facts aren't copyrightable; specific code is.
This commit adds one component: IsaacRandom — AC's variant of Bob
Jenkins' ISAAC PRNG, used to XOR a keystream into the CRC field of
every outbound packet for authentication. Clean-room reimplementation
based on reading:
- references/ACE/Source/ACE.Common/Cryptography/ISAAC.cs (AGPL oracle)
- Bob Jenkins' public ISAAC algorithm description
Implementation notes:
- 256 uint32 mm[] state, 256 uint32 rsl[] output buffer, a/b/c regs
- Initialize() runs 4 golden-ratio Mix() warmup rounds then two fold-in
passes over rsl[] and mm[] (fresh instance → both start as zeroes)
- AC variant: seed is exactly 4 bytes, interpreted as little-endian
uint32 assigned to a = b = c before the first Scramble()
- Scramble() produces 256 output words in one pass; Next() consumes
them backwards from offset 255 → 0, re-scrambling at offset -1
- Test seed 0x12345678 matches ACE's reference output byte-for-byte
across the first 16 values (golden vectors transcribed from a
throwaway oracle harness that compiled ACE's ISAAC.cs and printed
its output; the harness was deleted after extracting the values)
Tests (5, all passing):
- Next_Seed12345678_MatchesAceGoldenVectors: 16 golden uint32 values
- Next_TwoInstancesSameSeed_ProduceIdenticalSequence: 1000 outputs
- Next_DifferentSeeds_ProduceDifferentFirstOutput
- Next_512Calls_SpansTwoScrambleBatches: >400 distinct values in 512
outputs (catches all-zero / stuck-at-one bugs at scramble boundary)
- Ctor_ShortSeed_Throws
Both test projects still green: 77 core + 5 net = 82/82.
Phase 4.2 (packet framing + checksum) next.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Erik