How Team connects

The website is only a meeting point. When you host, it gives you a code. When a friend types that code, it tells each of you where the other one is. That takes a few seconds. After that your PCs talk straight to each other, and the website never sees your files, scenes or chat.

When you click Host a session or Join, the SDK spends up to 4 seconds on three things at once:

• Opens a port. One UDP port, 47320 unless you change it in the Host or Join window. If that's taken it uses any free one. Every friend in the session uses this same port.
• Asks for your internet address. It asks a STUN server (Google's or Cloudflare's) what your address looks like from outside. That's the address your friends will knock on.
• Asks your router to open the port (UPnP). Lots of routers say no, and that's fine. Step 3 usually gets through anyway.

It also notes your address on your home network, so two people on the same Wi-Fi can connect without going out to the internet and back.

Four small pages on reqid.io do the swapping. They're open and free. No account, no access code.

Codes, secrets and keys

• The code is 6 characters. Letters and numbers that look alike (0 and O, 1 and I) are left out, and spaces or dashes you type are ignored.
• The secret proves it's really the host checking for friends. The server only keeps a scrambled (hashed) copy.
• The key is a random token made with the session. Both PCs put it in every hello, so they only answer each other.
• The password is optional. The server only keeps a hashed copy and turns away a wrong one.

How long it lasts

• A code lasts 10 minutes after the last check, and 30 minutes at most. The SDK quietly gets a new one when it runs out (see step 6).
• One internet connection can start 12 sessions an hour. 20 wrong codes or passwords locks it out for 10 minutes.
• Old sessions are deleted automatically.

Now both PCs know a few addresses for the other one. They each send a tiny hello to all of them, 5 times a second. Most home routers block messages from strangers but allow replies to messages you sent. Since both sides send at the same time, each router sees the other's hello as a reply and lets it in. This is called hole punching.

Addresses tried, in order

• Your home network address, first, if the website saw you both coming from the same internet connection.
• Your internet address from step 1.
• The address the website saw you on, in case step 1 didn't get an answer.
• The home network address, last, for everyone else.

After 2 seconds with no answer it also tries the next 12 ports up, twice a second. Some routers change your port for each new contact, and this catches most of them.

After 15 seconds your friend sees an error and can click Join again. Your session stays open, and the chat says they couldn't get through.

A hello is one small message. Whoever gets a good one answers “got it”, and both sides switch to the real connection.

What gets checked

• Code and key match (or the password does).
• Same Team version. If not, your friend is told which version each of you has, and the host gets a note in chat. Nobody ends up half-connected.
• Room left. If the host already has 3 friends in, the newcomer is told the session is full.

Each friend now has a direct connection to the host. It runs on its own, so it keeps going while Unity is busy importing.

• Messages are cut into pieces of 1,200 bytes or less, so they fit through VPNs like Tailscale.
• Every piece is confirmed. Anything lost is sent again, in order. Camera positions are the exception: an old one is useless, so they're just sent fresh.
• It speeds up when the line is clear and slows down when pieces start getting lost.
• Big files are compressed when that makes them smaller.
• A tiny check goes out every second. That's where the ping in the Team tab comes from. 12 seconds of silence means the line dropped (see step 7).

A session holds 4 people: the host and 3 friends. Friends only connect to the host. The host passes everything on (edits, files, chat, cameras, selections), so friends never have to get through each other's routers.

• The code keeps working. While there's room, the host keeps checking the website every second. Each new friend goes through steps 2 to 4 the same way.
• One port for everyone. The host's port sorts each incoming message to the right friend.
• Everyone knows who's here. When someone joins or leaves, the host sends everyone the new list of people.
• New code after 30 minutes. When a code runs out, the host gets a new one and shows it. People already in aren't affected.

If two people join in the exact same second, one of them might get “Could not connect”. Just click Join again.

None of this goes back through the website. The two PCs send hellos to the last address that worked until they hear each other, then pick up where they left off. Anything not confirmed yet gets sent again.

For friends on the same network, or on Tailscale (free). In the Host or Join window, pick Same home network or Tailscale instead of Over the internet. The host gets a code, an address and a port, and friends type those in. That skips steps 1 and 2 and goes straight to the hello. The host checks the password, then makes up its own key.

The connection is direct, so everyone in a session can see each other's IP address. Only team up with people you trust, or use Tailscale.