network issue in one docker compose with keycloak and tomcat container - docker-compose

Question

Greeting,
I'm a beginner is learning web authentication, and would like to try with tomcat and keycloak in docker compose. I put them in one docker-compose.yml as follows:
version: '2'
services:
postgres:
image: postgres
ports:
- "5432:5432"
environment:
POSTGRES_DATABASE: 'keycloak'
POSTGRES_USER: 'keycloak'
POSTGRES_PASSWORD: 'keycloak'
POSTGRES_ROOT_PASSWORD: 'test'
volumes:
- ./postgres:/mnt/shares/postgres
keycloak:
image: jboss/keycloak-postgres
ports:
- "800:8080"
links:
- postgres
environment:
POSTGRES_PORT_5432_TCP_ADDR: 'postgres'
POSTGRES_DATABASE: 'keycloak'
POSTGRES_USER: 'keycloak'
POSTGRES_PASSWORD: 'keycloak'
KEYCLOAK_USER: 'admin'
KEYCLOAK_PASSWORD: 'admin'
POSTGRES_ROOT_PASSWORD: 'test'
depends_on:
- postgres
volumes:
- ./keycloak:/mnt/shares/keycloak
tomcat_keycloak:
build: .
ports:
- "880:8080"
volumes:
- ./web:/mnt/shares/web
- ./scratches:/mnt/shares/scratches
This can launch fine. Next I created the realm, client, and user in the keycloak, obtained a keycloak.json for tomcat as follows:
{
"realm": "TestRealm",
"auth-server-url": "http://192.168.208.130:800/auth",
"ssl-required": "external",
"resource": "test-client",
"public-client": true,
"use-resource-role-mappings": true
}
where 192.168.208.130 is my host ip address. Then I tried a static web link in my tomcat server. I could be redirected to the keycloak login page. But after entering user name and password, I got HTTP status 403. In the keycloak events I saw the logon was successful, and a session was established. I checked the tomcat output, and then found the following:
07-Apr-2017 17:37:04.240 INFO [http-apr-8080-exec-4] org.apache.http.impl.client.DefaultHttpClient.tryConnect I/O exception (java.net.NoRouteToHostException) caught when connecting to {}->http://192.168.208.130:800: No route to host (Host unreachable)
Looks like from my tomcat container, I cannot do HTTP client connection to my keycloak server container via the URL in host ip address. I can ping the host ip from the tomcat container though.
Could you help me to find out what I'm missing in this configuration? Really appreciate.