Port already in use

I get an error saying my port is already in use when starting mosquitto

root@OpenHAB:~# mosquitto -v
[393656.339556]~DLT~23300~INFO     ~FIFO /tmp/dlt cannot be opened. Retrying later...
1619595270: mosquitto version 1.6.9 starting
1619595270: Using default config.
1619595270: Opening ipv4 listen socket on port 1883.
1619595270: Error: Address already in use

I configured the port as follows:
lxc config device add OpenHAB myport1883 proxy listen=tcp:0.0.0.0:1883 connect=tcp:127.0.0.1:1883

The port configuration says:

simon@ansi-itx:~$ sudo lsof -i -n | grep 1883
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lsof: no pwd entry for UID 1000000
lxd       3227629         1000000    3u  IPv6 13871533      0t0  TCP *:1883 (LISTEN)
lxd       3227629         1000000    8u  IPv6 13871533      0t0  TCP *:1883 (LISTEN)
simon@ansi-itx:~$ sudo lxc exec OpenHAB -- /bin/bash
root@OpenHAB:~# sudo lsof -i -n | grep 1883
mosquitto  207       mosquitto    7u  IPv4 13249724      0t0  TCP *:1883 (LISTEN)
mosquitto  207       mosquitto    8u  IPv6 13249729      0t0  TCP *:1883 (LISTEN)
mosquitto  207       mosquitto    9u  IPv4 13464490      0t0  TCP 127.0.0.1:1883->127.0.0.1:35182 (ESTABLISHED)
java      6432         openhab  398u  IPv6 13465202      0t0  TCP 127.0.0.1:35182->127.0.0.1:1883 (ESTABLISHED)

I know this it not completely lxd related, but probably someone can help me here.