How to run inside Docker and connect from outside the host?

[spietras]

If I understand correctly, WebRTC data connection is based on UDP and therefore the server needs to be directly reachable from the client. So all following scenarios should work out of the box:

• client on localhost, server on localhost
• client on localhost, server inside Docker container with bridge network (because host can access container address directly)
• client on localhost, server inside Docker container with host network (this is basically the same as first one)
• client on LAN, server on localhost
• client on LAN, server inside Docker container with host network (also same as the one above)

But consider this scenario:

• client on LAN, server inside Docker container with bridge network

Let's say our (server host) address on LAN is 192.168.1.2, client is on 192.168.1.3 and server is inside Docker container with address 172.17.0.2. So our machine is visible to the client as 192.168.1.2, but the server address 172.17.0.2 is only understandable by our host, client doesn't know anything about it. But if we run the server inside Docker container (in bridge mode), expose its ports (for simplicity let's say it's the default 3000/tcp and 20000-20100/udp), connect from the client to the host at 192.168.1.2:3000, we will get 172.17.0.1 (Docker gateway) as ICE candidate sent to the client! But the client has no clue what this is, so it can't connect to it.

I might be wrong somewhere as I have trouble understanding all the networking stuff, but I stumbled upon this problem when testing geckos inside Docker on LAN. If we switch to host network mode then it's all fine as the server is directly on host, but I think this is not a satisfying long-term solution.

Do you know any way of achieving connectivity while using bridge network with Docker? Maybe some local STUN server is needed?