@Override
    public boolean isConnected(final Endpoint endpoint) {
        final RpcClient rc = this.rpcClient;
        return rc != null && isConnected(rc, endpoint);
    }
Abstract RPC client service based.
@author boyan (boyan@alibaba-inc.com)
@author jiachun.fjc
jraft-core/src/main/java/com/alipay/sofa/jraft/rpc/impl/AbstractClientService.java