public void start() throws IOException {
    int rpcHandlerCount = conf.getInt(ProxyConfig.PROXY_HANDLER_COUNT, ProxyConfig.PROXY_HANDLER_COUNT_DEFAULT);
    RPC.setProtocolEngine(conf, ClientNamenodeProtocolPB.class,
            ProtobufRpcEngine.class);
    RPC.setProtocolEngine(conf, NamenodeProtocolPB.class,
            ProtobufRpcEngine.class);

    this.protocol = (ClientProtocol) Proxy.newProxyInstance(
            this.getClass().getClassLoader(),
            new Class[]{ClientProtocol.class},
            this.invocationHandler);

    ClientNamenodeProtocolPB proxy = new ClientNamenodeProtocolServerSideTranslatorPB(this.protocol);
    BlockingService clientNNPbService = ClientNamenodeProtocolProtos.ClientNamenodeProtocol.
            newReflectiveBlockingService(proxy);

    int port = conf.getInt(ProxyConfig.RPC_PORT, ProxyConfig.RPC_PORT_DEFAULT);

    this.rpcServer = new RPC.Builder(conf)
            .setProtocol(org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolPB.class)
            .setInstance(clientNNPbService).setBindAddress("0.0.0.0")
            .setPort(port).setNumHandlers(rpcHandlerCount)
            .setVerbose(false).build();
    this.rpcServer.start();

    InetSocketAddress listenAddr = rpcServer.getListenerAddress();
    rpcAddress = new InetSocketAddress("0.0.0.0", listenAddr.getPort());
}