FIX 4.4

Pulse exposes its simulated exchange as a FIX 4.4 acceptor over raw TCP. Your algo logs on with its own FIX engine, starts a simulation, subscribes to the book, and sends orders into the live agent-based market — the same message types it would speak to a real venue. Nothing in your order-entry code needs to know it is talking to a simulation.

For why you would do that rather than submit a batch job, see the FIX overview. This page is the technical reference: connection details, identity, the message set, and the custom tags.

Connecting

The acceptor is a plain TCP listener, not an HTTP endpoint, so it sits on its own address rather than behind the API host.

Ask support@simudyne.com for the venue address and to have your account enabled for FIX.

Identity and authentication

Your CompID is your user_id

There is nothing to provision and no second credential to keep in step. Your SenderCompID is your Pulse account id, which you can read straight off your profile:

me = client.profile.get()

print(f"SenderCompID: {me['user_id']}")
print(f"tier: {me['tier']}")

SenderCompID: user_76b8ee0fe28cdbbf42ebc0e763c76750
tier: pro

The venue's CompID

Set TargetCompID to PULSE. The venue announces that name on every message it sends you, so a session configured for a different venue cannot log on by accident.

TargetCompID (56) = PULSE

The API key rides in the Logon

Put your Pulse API key in Password(554) on the 35=A Logon. A FIX credential is presented once and the session then lives for hours, so this is the only point at which you prove who you are — a rejected logon refuses the session outright rather than letting an unknown client trade.

8=FIX.4.4|35=A|49=user_76b8ee0f…|56=PULSE|98=0|108=30|554=pk_live_…|

Why a logon is rejected

A session, end to end

The one step that is easy to miss is the first: you must start a simulation before there is any market to subscribe to. A 35=V sent before that comes back as 35=Y MarketDataRequestReject.

Message set

Orders

40=2 Limit with a price in 44 rests in the book. Anything else — including an omitted OrdType — is treated as a market order and executes against resting liquidity immediately.

Custom tags

The venue permits user-defined fields, and uses them to carry the simulation parameters FIX has no standard field for. These go on 35=g:

Use calibrated_data() to pick a symbol, provider, exchange and cal_date combination that is actually calibrated, and list_scenarios() for the scenario names.

Outbound

Speed

Send 35=g again on a running session with a new 20001 to change speed mid-simulation. Around 10× is what the engine sustains in practice — above that the clock is limited by how fast the market can actually be generated, not by the throttle.

The end-of-session cost report

When the simulation ends, the final 35=h Closed carries your execution costs, measured against a baseline twin of the same simulation that never saw your orders. That is what makes the number meaningful: it is the cost of your flow specifically, not of the day.

The same figures also arrive as JSON in Text(58) on that message, so a client that does not want to read custom tags can parse one field instead. The batch equivalent is exec_results.parquet — see Execution algorithms.

What you have run

The venue records the shape of every session it starts, which you can read back over HTTP with client.fix.usage(). Only the parameters are kept — symbol, date, scenario, speed, horizon. No orders, no schedules, no fills: that is your strategy, and it is not stored.

usage = client.fix.usage()

print(f"{usage['total_runs']} FIX runs, "
      f"{usage['simulated_seconds']:.0f} simulated seconds")

for run in usage["runs"][:5]:
    print(f"  {run['symbol']} {run['cal_date']} {run['scenario']}: "
          f"{run['runs']}x")

12 FIX runs, 37800 simulated seconds
  1024 2025-09-01 normal: 9x
  1024.HK 2025-10-14 normal: 1x

Getting access

You need a Pro or demo tier account, an API key, and the venue address. Email support@simudyne.com telling us which system you want to connect and we will confirm the address and check your account has a session declared.