It's in the docker folder this script file start.sh. It does a replacment of the IP address in one of the configuration files of the node.js code. If you take a complete zip of Tony's repository:
Unzip it on a pi that has docker-compose, then go into the docker folder you will file the shell script. The docker-compose up -d will build a new container image with all the node.js stuff and start it. You should then be able to use the ip address of your pi and the right address will be sent to the Echo Speaks speaks for it's configuration.
#!/bin/bash
# I added the line below and give it the Pi's IP Address
IPADDRESS=192.168.20.251
if [[ (-z "${IPADDRESS}") ]]; then
echo "Please set IPADDRESS environment variables"
echo "example: IPADDRESS=192.168.1.100 ./start.sh"
exit 1
fi
if [ $(grep -c "IPADDRESS_TO_CHANGE" env.echo-speaks-server.dist) -ne 0 ]; then
sed "s/IPADDRESS_TO_CHANGE/$IPADDRESS/g" env.echo-speaks-server.dist > env.echo-speaks-server
fi
echo "Starting docker-compose"
docker-compose up -d