FIX API for forex brokers
FIX (Financial Information eXchange) is the standard protocol liquidity providers and brokers use to exchange prices, orders and fills. Almost all FX and CFD liquidity is streamed over FIX 4.4, so every broker connecting an LP meets it.
How a FIX session works
A FIX connection is a long running session over TCP, kept alive and kept in order by a few simple rules.
- 01
Log on
Your side connects and sends a Logon with its CompIDs and heartbeat interval. The LP answers with its own Logon.
- 02
Stay in step
Every message carries a sequence number. A gap triggers a resend request, so nothing is silently lost.
- 03
Stay alive
When there is nothing to say, each side sends a heartbeat. Silence past the interval gets a test request, then a disconnect.
- 04
Reset
Sequence numbers reset on a schedule, often daily or weekly, and both sides must agree when.
The FIX 4.4 messages brokers meet
Each message type is identified by tag 35. A price connection uses the session messages and market data; a trading connection adds orders.
- LogonTag 35:35=AWhat it does:Opens the session. Carries SenderCompID (49), TargetCompID (56), the heartbeat interval (108) and often a username and password.
- HeartbeatTag 35:35=0What it does:Sent when nothing else has been sent for one heartbeat interval, so both sides know the link is alive.
- Test requestTag 35:35=1What it does:Asks the other side for a heartbeat when it has gone quiet. No answer means the session is dropped.
- Resend requestTag 35:35=2What it does:Asks for messages again after a gap in sequence numbers.
- Sequence resetTag 35:35=4What it does:Moves the expected sequence number on, used to fill gaps or after a scheduled reset.
- LogoutTag 35:35=5What it does:Closes the session cleanly, usually with a reason in the text field.
- Market data requestTag 35:35=VWhat it does:Subscribes to prices for one or more symbols, as top of book or several levels.
- Market data snapshotTag 35:35=WWhat it does:A full picture of the current prices for a symbol.
- Market data incrementalTag 35:35=XWhat it does:Only what changed since the last update. Many LPs stream this way.
- Market data rejectTag 35:35=YWhat it does:The subscription was refused, for example an unknown symbol.
- New order singleTag 35:35=DWhat it does:A new order, on trading sessions only.
- Execution reportTag 35:35=8What it does:Order accepted, filled, partly filled or rejected.
What to agree with an LP
Most failed first connections come from a mismatch in one of these. Get them in writing before anyone opens a port.
- 01
Spec and version
The LP’s FIX specification document and version, almost always FIX 4.4 for FX and CFD liquidity.
- 02
CompIDs and credentials
Your SenderCompID, their TargetCompID, and any username and password sent at logon.
- 03
IPs to allow-list
LPs accept connections only from known addresses, so you need a fixed IP that will not change.
- 04
Separate sessions
Most LPs give one session for prices and another for orders, each with its own CompIDs.
- 05
Heartbeat and resets
The heartbeat interval, and when sequence numbers reset: daily, weekly, or only on request.
- 06
Symbols and depth
The exact symbol names and suffixes, and whether you get top of book or several levels of depth.
- 07
Test environment
A UAT session to prove the connection before you touch production.
- 08
Support contacts
Who to call when the session drops, and what hours they answer.
Why FIX sessions drop
The four problems behind most support tickets.
Sequence number mismatch
After a restart or a missed reset, one side expects a different number and refuses the logon. Agree the reset schedule and how to recover.
Missed heartbeats
Network trouble or a busy server delays heartbeats, the other side sends a test request, and the session drops.
Logon refused
Wrong CompID, wrong password or an IP that is not on the allow-list. The logout text usually says which.
Logged in but silent
The session stays up and heartbeats flow, but prices stop. The hardest failure to spot without a watchdog.
In XiroLink
FIX 4.4 on both sides, watched for you
XiroLink connects to LPs over FIX 4.4 or TCP, each in its own session with its own heartbeat and reconnect, from your bridge’s own fixed IP so LPs allow-list one address. A silent feed watchdog spots an LP that stays logged in but stops quoting.
It follows Centroid’s FIX 4.4 specifications both ways, and can serve your own clients over FIX as takers with their own credentials, allowed IPs and spreads. XiroLink sessions carry prices; orders are not routed.
More terms such as Comp ID and heartbeat interval are in the glossary. For the whole setup from LP to MetaTrader, see how to connect a liquidity provider to MT5.
FIX questions
What is FIX API in forex?
FIX (Financial Information eXchange) is the standard protocol liquidity providers, brokers and institutional clients use to exchange prices, orders and fills. "FIX API" usually means a FIX session a provider offers for streaming prices, trading, or both.
Why is FIX 4.4 still so common?
Most FX and CFD liquidity providers built their interfaces on FIX 4.4 and kept them. FIX 5.0 splits the session layer into FIXT 1.1 and adds features, but FIX 4.4 remains the version you will meet most often.
What are SenderCompID and TargetCompID?
The identifiers each side uses in every message header (tags 49 and 56). Your SenderCompID is their TargetCompID and the other way round, and both must match what the LP set up, or the logon is refused.
Can I offer my own prices to clients over FIX?
Yes. With XiroLink you add a FIX taker with its own credentials, allowed IP ranges, symbol names and markup profile, and send the client a generated connection guide.
Do I need FIX to connect MetaTrader?
No. XiroLink connects to MT4 and MT5 through its datafeed plugins. FIX is for connecting LPs and for clients or systems that take prices over FIX.