Galera - why can't I use port 4567 for replication?

Question

I have two Galera clusters in two different datacenters.

I want to replicate cluster c1(using c1-1 node as replication master) to cluster c2 (using c2-1 node as replication slave). Everything works well if I use port 3306 on c2-1for MASTER_PORT instead of the default port for replication 4567.

If I switch from port 3306 to 4567 for MASTER_PORT I get this error when I run SHOW SLAVE STATUS\G on c2-1:

Last_IO_Errno: 2013
Last_IO_Error: error connecting to master 'repl@x.x.x.x:4567' - retry-time: 60  maximum-retries: 86400  message: Lost connection to server at 'reading initial communication packet', system error: 0 "Internal error/check (Not system error)"

This is what I get when I run lsof -i:3306 on c1-1:

root@c1-1:~# lsof -i:3306
COMMAND   PID  USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mariadbd 1402 mysql   31u  IPv4  25689      0t0  TCP *:mysql (LISTEN)

And this is what i get when i run lsof -i:4567 on c1-1 (same node):

root@c1-1:~# lsof -i:4567
COMMAND   PID  USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mariadbd 1402 mysql    8u  IPv4  25683      0t0  TCP *:4567 (LISTEN)

Also I allowed all traffic (using ufw) on all those ports.

If I run netcat x.x.x.x 3306 (x.x.x.x being c1-1's ip) on c2-1 I get this:

root@c2-1:~# netcat x.x.x.x 3306
q
5.5.5-10.5.9-MariaDB-1:10.5.9+maria~focal-log,)XbbFt8Z��-��:Srf(

And if I run netcat x.x.x.x 4567 (x.x.x.x being c1-1's ip) on `c2-1 I get this:

root@c2-1:~# netcat x.x.x.x 4567
$�-��\�цI�-Vk8�$

Why can't I use port 4567? Is it not using the right socket? If so what can be done?

Thank you!

Answer 1

4567 is the default Galera Replication Port for replication between nodes within a Galera cluster. That is not what you want to use here - you are doing primary-secondary replication (master-slave).

3306 is the default TCP/IP port you want to use for primary-secondary (master-slave) replication.