<datasource jndi-name="java:jboss/datasources/KeycloakDS" pool-name="KeycloakDS" enabled="true" use-java-context="true">
    <connection-url>jdbc:postgresql://{REMOTE_IP}:5432/keycloak</connection-url>
    <driver>postgresql</driver>
    <pool>
        <max-pool-size>20</max-pool-size>
    </pool>
    <security>
        <user-name>keycloak</user-name>
        <password>{PASSWORD}</password>
    </security>
</datasource>

...
Caused by: org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:262)
    at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:52)
    at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:216)
    at org.postgresql.Driver.makeConnection(Driver.java:404)
    at org.postgresql.Driver.connect(Driver.java:272)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at org.postgresql.ds.common.BaseDataSource.getConnection(BaseDataSource.java:86)
    at org.postgresql.ds.PGPoolingDataSource.getConnection(PGPoolingDataSource.java:309)
    at org.jboss.jca.adapters.jdbc.local.LocalManagedConnectionFactory.createLocalManagedConnection(LocalManagedConnectionFactory.java:312)
    ... 43 more
Caused by: java.net.ConnectException: Connection refused (Connection refused)
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at org.postgresql.core.PGStream.<init>(PGStream.java:61)
    at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:144)
    ... 52 more

# psql -h {REMOTE_IP} keycloak keycloak
psql (9.5.7)
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384,
bits: 256, compression: off)
Type "help" for help.

keycloak=>