The class ProxyPeerAddressHandler always adds the port to the HOST header field. While it is allowed to always add the port, this breaks for example keycloak running behind a reverse proxy (https://issues.jboss.org/browse/KEYCLOAK-2830)

According to the HTTP specification (https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.23) the port can be left out, if it is the default port for the current schema (80 for HTTP and 443 for HTTPS).

Most (if not all) browser implement the HOST header this way, they only send the port if it is different from the default.