fixcore-engine 0.5.0

Pure Python FIX protocol engine

Pure Python FIX protocol engine — mirrors the QuickFIX architecture (QuickFIX/n, QuickFIX/J).

Features

• Full FIX 4.2 session layer (Logon, Logout, Heartbeat, TestRequest, ResendRequest, SequenceReset, Reject) with gap-fill, out-of-order buffering, and reset handling
• Message encode/decode (checksum, BodyLength, field-order validation) and repeating groups
• Opt-in per-session validation against a QuickFIX DataDictionary — required fields and out-of-range enum values, with spec-compliant Rejects
• Async transport: SocketAcceptor + SocketInitiator with auto-reconnect
• Durable FileStore (fsync + atomic sequence-number writes) and MemoryStore
• MessageCracker dispatch mixin
• Lightweight browser GUI via aiohttp (tools/fix_gui.py) — session management, message builder, live message log

Quick start

pip install fixcore-engine
pip install "fixcore-engine[gui]"  # includes aiohttp for the GUI

Validation (opt-in)

Validation is off by default (raw FIX passthrough). Enable it per session via QuickFIX-compatible settings:

[SESSION]
UseDataDictionary=Y             ; load the spec: group-aware decode + (by default) validation
DataDictionary=specs/FIX42.xml
ValidateIncomingMessage=N       ; keep group-aware decode but DON'T reject non-conforming inbound (default Y)
ValidateFieldsOutOfRange=Y      ; also reject out-of-range enum values (e.g. Side=Z)

UseDataDictionary=Y loads the spec so repeating groups decode into proper instances. By default it also validates inbound app messages (required fields, known MsgType) and Rejects violations. Set ValidateIncomingMessage=N to keep the group-aware decode while delivering non-conforming messages as-is — useful for permissive/testing peers that need to inspect off-spec traffic rather than reject it.

Development

pip install -e ".[dev,gui]"
pytest
python tools/fix_gui.py