Yes, I saw this part of kamailio doc, and even I added this part in my.cnf:
[kamailio]
socket = /path/to/mysql.sock
user = kamailiouser
password = kamailiopass
default-character-set = utf8

(with valid password) it didn't help me (of course I restarted the mysqld).

Both of the following syntax worked fine for me:
# mysql --user=xxx --password=xx --host=localhost --protocol=tcp <database>
# mysql --user=xxx --password=xx --protocol=socket <database>

So that, I could get into a mysql console (with kamailioro user/pasword).

I mentioned in a previous message, that Kamailio is installed from repository and is not compiled.
But, kamailio-mysql-modules:amd64 is installed.

So looks, like there is no problem with socket connection, because kamailio doesn't say that problem depends on mysql module, it said that problem consists of accessing for kamailioro user.

>Hi,
>
>So, I have not been using Kamailio with MySQL before, but I do have
>some basic MySQL knowledge.
>
>MySQL can be used with both socket and TCP, have you verified that
>your setup is matching the server setup.
>
>Have you look at this section:
>https://kamailio.org/docs/modules/4.3.x/modules/db_mysql.html#idp3037648
>
>You can also test/check that socket/tcp is working by testing it like this:
># mysql --user=xxx --password=xx --host=localhost --protocol=tcp <database>
># mysql --user=xxx --password=xx --protocol=socket <database>
>
>
>On Fri, May 5, 2017 at 4:47 PM, Донат Зеничев <donat.zenichev at gmail.com> wrote:
>> Hi.
>>
>> I have just written routing logic for my new sip-proxy server, but have a
>> problem with start of kamailio.
>>
>> ./kamailio.cfg file has no mistakes - it's made well done.
>>
>> before to start coding with routing logic, of course I installed kamailio
>> (ver 4.3.4) from repository.
>> OS - ubuntu 16.04
>>
>> and add next modules from repository:
>> kamailio-mysql-modules:amd64
>> kamailio-perl-modules:amd64
>> kamailio-radius-modules:amd64
>> kamailio-tls-modules:amd64
>> kamailio-utils-modules:amd64
>>
>> next step, I edited the ./kamctlrc file to contain proper user/password and
>> mysql engine settings.
>> And than, ran the kamdbctl create (without special parameters).
>>
>> A bit about my kamailio.cfg :
>> fork=yes
>> children=4
>> disable_tcp=no
>> tcp_children=4
>> tcp_send_timeout=3
>> tcp_connect_timeout=5
>> tcp_connection_lifetime=3600
>> tcp_max_connections=4096
>>
>> of course mpath is defined and proper modparams (depending on my ver) for
>> modules are used.
>>
>> A bit about my kamctlrc:
>> Ro and rw user are defined (and connections to needed db from these users is
>> checked, as like it was real kamailio that tries to update some values in db
>> - well done).
>>
>> Also PID_FILE and FIFOPATH are defined (/var/run/kamailio dir. created)
>>
>> So that, now I'm trying to start the server as a daemon, I have the
>> following row in systemctl:
>> ERROR: db_mysql [km_my_con.c:124]: db_mysql_new_connection(): driver error:
>> Access denied for user 'kamailioro'@'localhost' (using password: YES)
>>
>> And of course all other modules can't run because they depend on the db
>> connections.
>> So looks like very simple problem, just need to edit mysql user table to
>> have proper passwords.
>>
>> But I've refurbished ro and rw user several times, it didn't help me.
>> Also tried to drop kamailio db with db users and run kamdbctl create again -
>> nothing changed.
>>
>> I tried to find where kamailioro user can be defined as default, but didn't
>> find any files (apart of kamctlrc in /etc/kamailio directory).
>> /etc/default/kamailio file contains proper values and paths.
>>
>> Please advise something.
>>
>>
>>
>> --
>> --
>> BR, Donat Zenichev
>> Wnet VoIP team
>> Tel:  +380(44) 5-900-808
>> http://wnet.ua
>>
>> _______________________________________________
>> Kamailio (SER) - Users Mailing List
>> sr-users at lists.kamailio.org
>> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
>>
>
>
>
>-- 
>Best regards,
>
>Glenn O. Larsen

--
-- 
BR, Donat Zenichev
Wnet VoIP team
Tel:  +380(44) 5-900-808
http://wnet.ua