mosquitto PSK Encryption not working - mosquitto

Question

I'm trying to build a PSK Encryption bridge connection with mosquitto following this tutorial. I'm using two docker containers. One as a bridge and another one as a server. Both of them on different computers. The connection works fine with no encryption. For the subscriptions to the topics I'm using node-red.
This is the configuration file for the server:
port 1883
persistence true
persistence_location /mosquitto/data/
#persistence_file mosquitto.db
#cleansession false
#clientid nodered
listener 8883
psk_hint broker-server
psk_file /mosquitto/certs/psk_file.txt
log_type all
log_dest file /mosquitto/log/mosquitto.log
connection_messages true
log_timestamp true
allow_anonymous true
#password_file /mosquitto/config/passwd
For the bridge connection I have to files.
mosquitto.conf:
#include_dir /etc/mosquitto/conf.d
# GENERAL CONFIGURATION BROKER
# ----------------------------------------------------------------
pid_file /var/run/mosquitto.pid
persistence true
persistence_location /var/lib/mosquitto/
log_type all
log_dest file /etc/mosquitto/log/mosquitto.log
include_dir /etc/mosquitto/bridges
# ----------------------------------------------------------------
# SECURITY (comm. Nordic -> RPI): Password
#password_file /etc/mosquitto/passwd
allow_anonymous true
And bridge.conf:
# =================================================================
# Bridges to Node Red
# =================================================================
# IP address
#connection client-bridgeport
connection bridge-01
address 192.168.1.34:8883
bridge_identity bridgeport
bridge_psk 123456789987654321
# -----------------------------------------------------------------
# TOPICS
topic # out 1 ""
topic # in 1 ""
# ------------------------------------------------------------------
# Setting protocol version explicitly
#bridge_protocol_version mqttv311
#bridge_insecure false
# Bridge connection name and MQTT client Id,
# enabling the connection automatically when the broker starts.
cleansession false
remote_clientid broker-server
start_type automatic
#notifications false
log_type all
In the logfile of the server I can see the following error:
Socket error on client unknown, disconnecting.
And in the bridge connection I see the following error:
Bridge broker-server sending CONNECT Socket error on client
local.broker-server, disconnecting.
I don't know what I'm doing wrong. If I remove the encryption everything works fine.

Answer 1

It seems that the default docker container of mosquitto in docker hub has not included the psk encryption in the mosquitto build as is shown in this post.
I had to build my own image installing mosquitto as following:
RUN apt-get -y update && \
apt-get -y install mosquitto mosquitto-clients