mjhjmtu

I'm trying to use socat as a UDP proxy (v4->v6) for a client (game) which routinely initiates new UDP "connections" (TL;DR - the world runs on multiple servers listening on different UDP ports, client stays connected to 1 particular server, and will need to connect to another, as the player travels between world layers). As I understand the manual, the "fork" option should take care of this, keeping the listening socket in the parent process and forking off children bound to specific "remote" address + port:

$ socat UDP4-LISTEN:11001,bind=127.0.0.1,fork,reuseport,reuseaddr UDP6-SENDTO:remotehost:11001
(repeated for port 11000)

So far, so good:

$ lsof -P -i 4UDP -a -p $(pgrep -d, socat)
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
socat 2990 myxal 5u IPv4 0x4e6e342add34664f 0t0 UDP localhost:11001
socat 2991 myxal 5u IPv4 0x4e6e342add345f2f 0t0 UDP localhost:11000

But when I actually do this and run the client, the parent that should reopen the listening socket fails with "Address already in use":

socat[2990] E bind(5, LEN=16 AF=2 127.0.0.1:11001, 16): Address already in use

Of course, lsof confirms there's nothing listening on that socket:

$ lsof -P -i 4UDP:11001
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
socat 3105 myxal 5u IPv4 0x4e6e342add34664f 0t0 UDP localhost:11001->localhost:57324

I can even run nc -u -l 11001 at this point without issue. What am I missing here?

EDIT: I'm starting to think the command above is technically correct, and I'm seeing a bug in socat. ATM, I'm working around the issue by simply launching socat in a loop - the children which hold the connected socket, are unaffected, after all...

while true; do sleep 1; socat [...] ;