SimHub and CrewChief at the same time: fixing UDP conflicts
Last updated · SimHub 9.11.22
A game that broadcasts telemetry over UDP sends it to one port, and only one application can receive it — whichever claims the port first. That is why SimHub goes blank when you launch CrewChief, or vice versa. The fix is UDP forwarding: one application receives the stream and re-broadcasts it to other ports or IP addresses, so everything downstream gets a copy. SimHub can do the forwarding, which makes it the natural first receiver in a chain.
This affects the UDP games only — the Forza titles, the F1 and Codemasters games, Project CARS, Gran Turismo. Shared-memory games like Assetto Corsa and iRacing are unaffected, because any number of applications can read the same memory region.
Why this happens
When a game sends telemetry over UDP, it addresses packets to a port number on a machine. An application that wants that data asks the operating system to hand it everything arriving on that port.
The operating system will normally grant that to one application. The second one to ask either gets an error or gets nothing — and most telemetry tools do not report this clearly, so what you see is a working dashboard that goes blank the moment you open something else.
This is not a SimHub bug and it is not CrewChief's fault. It is how UDP delivery works. Any two applications wanting the same stream on the same port will collide, in any combination. Blaming one of them is the reason people uninstall and reinstall things that were never broken.
Shared-memory games avoid the problem entirely: the game publishes a memory region and any number of readers can look at it simultaneously. That is why nobody ever reports this with iRacing or Assetto Corsa.
You do not have to take our word for any of this — SimHub says it on the configuration screen itself, next to the port you are setting:
SimHub’s own wording, on every UDP game’s telemetry tab: “This game uses UDP telemetry, UDP requires to choose an UDP port. Warning a single UDP port can be read by a single application at a time.”
Recognising it
- Telemetry works until you launch a second tool, then stops in one of them.
- Whichever application you start first is the one that keeps working.
- It only happens in some games — the UDP ones — and never in others.
- Closing the second application restores the first, sometimes only after a restart.
- Nothing in either application's settings looks wrong, because nothing is.
That third point is the strongest signal. If Assetto Corsa is fine and Forza is not, you are looking at a UDP conflict rather than a configuration problem.
The fix: UDP forwarding
SimHub can act as a repeater. It receives the game's stream on the expected port, uses it, and re-broadcasts the same packets to other ports and IP addresses. Downstream applications listen to those instead of to the game.
The controls are on the same Telemetry tab as the port itself, under UDP forwarding — a toggle, a destination port, an IP address, and an Add forward target link for sending to more than one place. SimHub’s description of it: “Forwarding UDP data will allow you to feed an additionnal application running on the same computer (127.0.0.1) or a remote computer/device, make sure to configure it on the port defined here.”
Decide the chain
One application receives from the game; everything else receives from that one. SimHub is the natural first link because forwarding is built in.
Point the game at SimHub
In the game's telemetry settings, set the destination to your PC and the port SimHub expects. If SimHub and the game are on the same machine,
127.0.0.1is the address.Enable forwarding in SimHub
In the game's settings inside SimHub, turn on UDP forwarding and add a destination — an address and a port that nothing else is using.
Point the second application at the forwarded port
Configure CrewChief, Track Titan or whatever else to listen on that port rather than on the game's original one.
Start SimHub first
The receiver has to have the port before anything else asks for it. Making SimHub start with Windows removes this from your list of things to remember.
More than two applications works the same way — forward to several destinations, each on its own port.
Choosing ports
- Use ports above 20000 for forwarded streams. It keeps you clear of the defaults that other tools assume.
- Give each destination its own port. Two applications on one forwarded port recreate exactly the problem you are solving.
- Write down what you assigned. Six months later, a forwarded port with no record is confusing to rediscover.
- Keep away from 8888 and 8889, which SimHub uses for the phone dashboard web server.
For reference, Gran Turismo 7 uses ports 33739 and 33740 — those are the game's own, not something you choose.
Consoles make this more likely, not less
Console telemetry is UDP by definition — it is the only way data leaves the console. So every console setup is a UDP setup, and every console user who wants two tools needs forwarding.
The one difference: the game is broadcasting to your PC's address across the network rather than to 127.0.0.1. Set the destination IP in the console game's telemetry settings to your PC's address, and give the PC a fixed address in your router so it does not change on the next reboot and quietly break everything.
Details on SimHub on PS5 and Xbox.
Common questions
Where is UDP forwarding in SimHub?
On the Telemetry tab of a game’s Game Configuration dialog, directly under the UDP port setting. There is a toggle, a destination port, an IP address — 127.0.0.1 for another application on the same PC — and an Add forward target link for sending to more than one destination.
Can I run SimHub and CrewChief at the same time?
Yes, using UDP forwarding. SimHub receives the game's stream and re-broadcasts it to another port; CrewChief listens on that port instead of on the game's original one. Without forwarding, only whichever started first receives anything.
Why does SimHub stop working when I open another telemetry app?
Because only one application can receive a UDP stream on a given port. The second one to ask gets nothing. It affects UDP games only — Forza, F1, Codemasters titles, Project CARS, Gran Turismo — and never shared-memory games.
Why doesn't this happen with iRacing or Assetto Corsa?
They use shared memory rather than UDP. The game publishes a memory region and any number of applications can read it at once, so there is nothing to contend for.
Which application should receive the stream first?
SimHub, because forwarding is built in — that makes it the natural head of the chain. It also has to actually start first, since the port goes to whoever asks first. Starting SimHub with Windows removes the ordering problem.
What port should I forward to?
Anything above 20000 that nothing else uses, with a separate port per destination. Avoid 8888 and 8889, which SimHub's phone dashboard web server uses.
Does UDP forwarding add lag?
Negligibly. It is a packet copy on the same machine or the same local network. Any delay it adds is far below what you could perceive through a dashboard or a shaker.
Sources
Related guides
SimHub is developed independently by Wotever and is not affiliated with oesimracing. This page was checked against SimHub 9.11.22 on 4 August 2026; where the interface has moved on since, the version stamp tells you how far. More on what SimHub is and what it costs.