Prime FIX Testing Daemon

A FIX testing daemon that simulates Coinbase Prime's FIX gateway for local development and testing.

What This Is

A local testing tool that mimics Coinbase Prime's FIX API responses. Use it to develop and test FIX clients without connecting to production.

Simulates:

• Session management (Logon, Logout, Heartbeat, TestRequest, SequenceReset)
• Order entry (NewOrderSingle, OrderCancelRequest, OrderStatusRequest)
• Execution reports (fills, partial fills, cancellations, rejections)
• Market data snapshots (trades, order book, OHLCV)
• RFQ (Request for Quote)
• DropCopy sessions (read-only execution report streaming)

Does NOT provide:

• Real authentication (HMAC signatures are not validated)
• Real order execution (orders are simulated)
• Persistent state (everything is in-memory)
• Production parity (responses approximate but may differ from actual Prime)

Production-like behaviors:

• Rate limiting (50 requests/second per session)
• Proper FIX sequence number handling with message queuing during gaps
• Graceful cleanup of subscriptions on disconnect
• Thread-safe session and market data management

Installation

go build -o prime-fix-daemon ./cmd/daemon
go build -o fix-testclient ./cmd/testclient

Quick Start

# Terminal 1: Start daemon
./prime-fix-daemon

# Terminal 2: Start test client
./fix-testclient

Test Client Commands

The test client (fix-testclient) provides an interactive REPL for testing FIX functionality. All commands are documented below.

Order Entry

Command	Description
buy <symbol> <qty> [base|quote]	Market buy order. Default is quote quantity (USD amount)
sell <symbol> <qty> [base|quote]	Market sell order. Default is quote quantity (USD amount)
market <symbol> <buy|sell> <base|quote> <qty>	Explicit market order with quantity type
limit <symbol> <buy|sell> <qty> <price>	Limit order at specified price

Examples:

buy BTC-USD 100                # Buy $100 worth of BTC (quote quantity)
buy BTC-USD 0.001 base         # Buy exactly 0.001 BTC (base quantity)
sell ETH-USD 500               # Sell $500 worth of ETH
sell ETH-USD 0.5 base          # Sell exactly 0.5 ETH
market BTC-USD buy quote 1000  # Buy $1000 of BTC (explicit syntax)
market ETH-USD sell base 2.0   # Sell 2.0 ETH (explicit syntax)
limit BTC-USD buy 0.01 85000   # Limit buy 0.01 BTC @ $85,000
limit ETH-USD sell 1.0 4000    # Limit sell 1.0 ETH @ $4,000

Order Management

Command	Description
status <orderid|clordid>	Query order status by OrderID or ClOrdID
cancel <orderid> <origclordid> <symbol> <side> <qty>	Cancel an open order

Examples:

status abc123-def456           # Get status of order
cancel abc123 orig123 BTC-USD buy 0.01   # Cancel order

RFQ (Request for Quote)

Command	Description
rfq <symbol> <buy|sell> <qty> <limit_price>	Request a quote for a specified quantity

Examples:

rfq BTC-USD buy 0.5 90000      # Request quote to buy 0.5 BTC with limit $90,000
rfq ETH-USD sell 10 3500       # Request quote to sell 10 ETH with limit $3,500

Market Data

Command	Alias	Description
md <symbol> [trades|book|ohlcv]	-	Get market data snapshot (default: trades)
subscribe <symbol> [trades]	sub	Subscribe to streaming market data
unsubscribe <symbol>	unsub	Stop streaming market data

Examples:

md BTC-USD                     # Trade snapshot (default)
md BTC-USD trades              # Trade snapshot (explicit)
md BTC-USD book                # Order book snapshot (bids/offers)
md BTC-USD ohlcv               # OHLCV candle data (100 daily candles)
subscribe BTC-USD trades       # Start streaming trades (MsgType=X)
sub ETH-USD trades             # Alias for subscribe
unsubscribe BTC-USD            # Stop streaming
unsub ETH-USD                  # Alias for unsubscribe

Daemon Control (Runtime Configuration)

These commands change daemon behavior at runtime without restarting.

Command	Alias	Description
config	get-config	Display current daemon configuration
set-behavior <behavior>	behavior	Set default behavior for all orders
set-symbol <symbol> <behavior>	-	Set behavior for a specific symbol
clear-symbol <symbol>	-	Remove symbol-specific behavior (use default)

Behavior values: fill, partial, cancel, pending, reject

Examples:

config                         # Show current configuration
set-behavior reject            # All orders will be rejected
behavior fill                  # Alias: all orders will fill
set-symbol BTC-USD partial     # BTC orders partially fill
set-symbol ETH-USD reject      # ETH orders rejected
clear-symbol BTC-USD           # BTC uses default behavior again

Session Management

Command	Alias	Description
heartbeat	hb	Send a heartbeat message
logout	-	Send logout and disconnect gracefully
quit	exit	Send logout and exit the client
help	?	Display command help

Examples:

heartbeat                      # Send heartbeat
hb                             # Alias for heartbeat
logout                         # Graceful disconnect
quit                           # Exit client
help                           # Show all commands
?                              # Alias for help

Order Behaviors

Behavior	Description
fill	Order immediately fills completely
partial	Order partially fills in multiple executions
cancel	Order is accepted then canceled
pending	Order stays in pending/new state indefinitely
reject	Order is rejected immediately

Daemon Options

# Start the daemon (default settings)
./prime-fix-daemon

# Show help
./prime-fix-daemon --help

# Show version
./prime-fix-daemon --version

# Generate example config
./prime-fix-daemon generate-config

# Available flags:
#   -l, --listen string     Listen address (default ":4198")
#   -b, --behavior string   Default order behavior: fill, partial, cancel, pending, reject (default "fill")
#   -c, --config string     Path to configuration file
#       --heartbeat int     Heartbeat interval in seconds (default 30)
#       --tls               Enable TLS
#       --tls-cert string   TLS certificate file
#       --tls-key string    TLS key file
#       --reject-auth       Always reject authentication (for testing auth failures)

# Examples:
./prime-fix-daemon -l :5000 -b reject           # Custom port, reject all orders
./prime-fix-daemon -c config.json               # Use config file
./prime-fix-daemon --tls --tls-cert cert.pem --tls-key key.pem

Test Client Options

# Connect to default address (127.0.0.1:4198)
./fix-testclient

# Connect to custom address
./fix-testclient -a localhost:5000
./fix-testclient --addr 192.168.1.100:4198

# Show help
./fix-testclient --help

Configuration

Environment Variables

export FIX_FILL_SYMBOLS=BTC-USD,ETH-USD
export FIX_PARTIAL_SYMBOLS=SOL-USD
export FIX_CANCEL_SYMBOLS=DOGE-USD
export FIX_REJECT_SYMBOLS=SHIB-USD

JSON Configuration

./prime-fix-daemon generate-config    # Creates config.json
./prime-fix-daemon -c config.json     # Use config file

Supported Symbols

Only these symbols are accepted for orders, RFQ, and market data:

Symbol	Simulated Price
BTC-USD	$90,000
ETH-USD	$3,500
SOL-USD	$200
DOGE-USD	$0.40
XRP-USD	$2.20
ADA-USD	$0.90
AVAX-USD	$40
LINK-USD	$23

Requests for unsupported symbols are rejected with a BusinessReject (orders/RFQ) or MarketDataReject (market data).

FIX Protocol Details

• Version: FIX 4.2
• Server SenderCompID: COIN
• Default Port: 4198
• Heartbeat: 30 seconds

Supported Messages

MsgType	Name	Direction
A	Logon	Both
5	Logout	Both
0	Heartbeat	Both
1	TestRequest	Both
2	ResendRequest	Client → Server
4	SequenceReset	Server → Client
D	NewOrderSingle	Client → Server
F	OrderCancelRequest	Client → Server
H	OrderStatusRequest	Client → Server
R	QuoteRequest (RFQ)	Client → Server
S	Quote	Server → Client
V	MarketDataRequest	Client → Server
W	MarketDataSnapshot	Server → Client
X	MarketDataIncremental	Server → Client
8	ExecutionReport	Server → Client
9	OrderCancelReject	Server → Client
BE	UserRequest (Control)	Client → Server
BF	UserResponse (Control)	Server → Client

Connecting Your Own FIX Client

Configure your client to connect to localhost:4198:

[SESSION]
BeginString=FIX.4.2
SenderCompID=3e74e5c7-56a1-556a-b044-19936c5a728a
TargetCompID=COIN
SocketConnectHost=127.0.0.1
SocketConnectPort=4198
HeartBtInt=30

SenderCompID: This is your Service Account ID (a UUID) from Coinbase Prime. You can find it in the Prime web console under Settings > API. In production, each API key is tied to a specific portfolio and the SenderCompID identifies your session.

Note: This testing daemon does not validate authentication, so any UUID-formatted SenderCompID will work for local testing.

DropCopy Sessions

The daemon supports DropCopy sessions for testing clients that use separate order entry and execution report streaming connections. Up to 7 concurrent FIX sessions are supported.

How it works:

• A session becomes a DropCopy session when it sends DropCopyFlag=Y (tag 9406) in the Logon message
• DropCopy sessions receive copies of all execution reports from other sessions
• DropCopy sessions cannot submit orders or cancellations (rejected with BusinessReject)

Example Logon with DropCopy flag:

8=FIX.4.2|9=...|35=A|49=CLIENT|56=COIN|...|9406=Y|...