Switching from tcp://:port to quic://port


I have several devices in the LAN side so I use the tcp syntax in the title because IIUC, “default” can’t make better when it comes to remote connections.

If I switch to quic, do I have to change my pc firewalls & gateway settings from TCP to UDP (no upnp here)?

Also, when switched to quic, is UDP 21027 still useful for LAN broadcasts or are they done over the quic/UDP port, and should “Local discovery” setting remain enabled if we wanted it before?

Do remote devices in the clusters need quic too to connect to us?

Can I use this syntax for fallback: quic://:port,tcp://:port,dynamic+https://relays.syncthing.net/endpoint? Is a whitespace required after each comma?

Thank you

Why would you want to switch to quic on lan?

The order you give doesn’t matter, internally tcp still has priority over quic.

Hi Simon

This is not for LAN I’d like to change, it is for WAN for better connectivity to devices that are yet set to default. My questions about LAN (21027) are only there additionally to anticipate.

quic is enabled by default, you don’t need to change listening/devices settings.

As to the firewall: If I understand correctly, you shouldn’t need to change anything, as quic should work also in the presence of a firewall (assuming it allows outgoing connections, which is usually the case). @AudriusButkevicius : Please correct me if wrong.

You definitely shouldn’t disable local discovery or anything else, because as I said tcp connections (e.g. everything on your lan) are still the way to go. That also applies to WAN: If you control your firewalls/routers, you should enable port forwards (or upnp) to get a tcp connection.

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It does not work through all firewalls, it works through nats (which could be a firewall), and only certain types.

The point is I can’t use default (IIUC, see OP: more than 1 device on LAN side). Maybe we’d need a separate setting only for the port, e.g default,port=22001

Yes. No. :slight_smile:

We need a better listener configuration thing in general, outlined somewhere…

Many thanks you all. Please confirm: quic is UDP or TCP from netfilter POV ?


I still feel a bit confused: the documentation states:

Local firewall
Port 22000/TCP (or the actual listening port if you have changed the Sync Protocol Listen Address setting.)

To get quic working, should we read:

Port 22000/TCP+UDP (or the actual listening port if you have changed the Sync Protocol Listen Address setting.)

? If true, do it our gateway too.

Yes that predates QUIC. That said QUIC will often penetrate anyhow, by way of being bidirectional UDP over the same port.

Do you mean this is state of the art to open a port for both tcp and udp even when the documentation clearly states only one is used? Sorry if this is a silly question but I’m far from being an expert.

All the info is already in previous posts:

  1. Quic by default uses the same port, you can thus open both tcp/udp 22000 unless differently configured.
  2. Quic will probably work (or not) regardless of whether you open the port or not, it’s purpose is operation with restricted networking.
  3. If you can open the tcp port, quic is anyway not required. Simply put you can just totally forget about it. Tcp connections will be preferred.
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Thank you Simon. This is the ultimate answer :boom:

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