public int port(SessionProtocol protocol) {
        return delegate.port(protocol);
    }
Returns the port number of the {@link Server} for the specified {@link SessionProtocol}.

@throws IllegalStateException if the {@link Server} is not started or it did not open a port of the
                              specified protocol.
junit5/src/main/java/com/linecorp/armeria/testing/junit5/server/ServerExtension.java