[Bug] Client attempts to connect to UDP port 0

[AtomicByte8]

Summary

Possibly secondary to #182, the FiveM client will attempt to connect to UDP port 0 with the following server configuration:

endpoint_add_tcp "0.0.0.0:30120"
endpoint_add_udp "0.0.0.0:30120"

set sv_forceIndirectListing true
set sv_listingHostOverride "fivem.yourdomain.com"
sv_listingIpOverride "10.0.0.0"
sv_proxyIPRanges "10.0.0.0/24"
sv_endpoints "10.0.0.0:30120"

10.0.0.0 is a placeholder for a public IPv4 address.

All traffic forwarded to the backend server must originate from the same IP or the handshake will fail as described at #182

If all traffic is forwarded from the same IP, the handshake completes and the client reaches the "STARTING SESSION..." stage with the green progress bar at the bottom of the client. At this point, the client sends UDP traffic to 10.0.0.0:0 (port 0) and the connection fails with a timeout error.

Issue type

Both / Unsure

Repro rate

Always

Server build version

FXServer-early-access b94 win32

OS

No response

CPU

No response

GPU

No response

RAM

No response

Storage type

None

Connection type

None

ISP and bandwidth

No response

DxDiag

No response

Network graph

No response

Platform

Windows

OS version / distribution

No response

CPU

No response

RAM

No response

Using txAdmin?

None

Hosting provider

None

Machine type

None

/perf endpoint output

No response

DDoS protection

No response

ulimit -n value (Linux only)

No response

Docker Compose file (Docker only)

No response

Steps to Reproduce

1. Configure the server similar to this example:

endpoint_add_tcp "0.0.0.0:30120"
endpoint_add_udp "0.0.0.0:30120"

set sv_forceIndirectListing true
set sv_listingHostOverride "fivem.yourdomain.com"
sv_listingIpOverride "10.0.0.0"
sv_proxyIPRanges "10.0.0.0/24"
sv_endpoints "10.0.0.0:30120"

2. Attempt to connect using the server list.
3. The client will reach "STARTING SESSION..."
4. Sniff the traffic on the client or the server, you will see that the client is sending UDP packets to 10.0.0.0:0 (UDP port 0).

You will observe that the connection fails with a timeout error.

Connection failed
Connection lost. Timeout: true

Expected Behavior

The client should attempt to connect to UDP port 30120 as defined in endpoint_add_udp and sv_endpoints.

Actual Behavior

The client sends UDP traffic to port 0.

Evidence

No response

Additional Context

No response