xmemcached net.rubyeye.xmemcached.exception.UnknownCommandException

memcached是一个高性能分布式缓存系统，java一般通过xmemcached客户端实现与服务器端的数据交互，下面看一个奇怪的问题，代码如下：

]
public static void main(String[] args) throws IOException {
		MemcachedClientBuilder builder = new XMemcachedClientBuilder(
				AddrUtil.getAddresses("192.168.172.39:11211"));
		MemcachedClient client = builder.build();
		try {
			client.set("hello", 0, 1);
			System.out.println("获取设置的内容 = "+client.get("hello"));
			GetsResponse<Integer> result = client.gets("hello");
			long cas = result.getCas(); //获取当前cas
			System.out.println("当前cas = "+cas);
			//尝试更新hello成2
			if (!client.cas("hello", 0, 2, cas)){
				System.err.println("cas error");
			} 
		} catch (TimeoutException e) {
			e.printStackTrace();
		} catch (InterruptedException e) {
			e.printStackTrace();
		} catch (MemcachedException e) {
			e.printStackTrace();
		}
	}

最开始我的是memecached1.2.1，xmemcached2.0.0。运行main方法后报错，如下：

net.rubyeye.xmemcached.exception.MemcachedException: net.rubyeye.xmemcached.exception.UnknownCommandException: Response error,error message:Unknow command GETS_ONE,key=hello
	at net.rubyeye.xmemcached.XMemcachedClient.checkException(XMemcachedClient.java:1921)
	at net.rubyeye.xmemcached.XMemcachedClient.fetch0(XMemcachedClient.java:646)
	at net.rubyeye.xmemcached.XMemcachedClient.get0(XMemcachedClient.java:1058)
	at net.rubyeye.xmemcached.XMemcachedClient.gets(XMemcachedClient.java:1071)
	at net.rubyeye.xmemcached.XMemcachedClient.gets(XMemcachedClient.java:1093)
	at net.rubyeye.xmemcached.XMemcachedClient.gets(XMemcachedClient.java:1082)
	at com.zl.cache.city.CaseTest.main(CaseTest.java:22)
Caused by: net.rubyeye.xmemcached.exception.UnknownCommandException: Response error,error message:Unknow command GETS_ONE,key=hello
	at net.rubyeye.xmemcached.command.Command.decodeError(Command.java:251)
	at net.rubyeye.xmemcached.command.Command.decodeError(Command.java:279)
	at net.rubyeye.xmemcached.command.text.TextGetCommand.decode(TextGetCommand.java:127)
	at net.rubyeye.xmemcached.codec.MemcachedDecoder.decode0(MemcachedDecoder.java:61)
	at net.rubyeye.xmemcached.codec.MemcachedDecoder.decode(MemcachedDecoder.java:56)
	at com.google.code.yanf4j.nio.impl.NioTCPSession.decode(NioTCPSession.java:297)
	at com.google.code.yanf4j.nio.impl.NioTCPSession.decodeAndDispatch(NioTCPSession.java:237)
	at com.google.code.yanf4j.nio.impl.NioTCPSession.readFromBuffer(NioTCPSession.java:207)
	at com.google.code.yanf4j.nio.impl.AbstractNioSession.onRead(AbstractNioSession.java:196)
	at com.google.code.yanf4j.nio.impl.AbstractNioSession.onEvent(AbstractNioSession.java:341)
	at com.google.code.yanf4j.nio.impl.SocketChannelController.dispatchReadEvent(SocketChannelController.java:56)
	at com.google.code.yanf4j.nio.impl.NioController.onRead(NioController.java:157)
	at com.google.code.yanf4j.nio.impl.Reactor.dispatchEvent(Reactor.java:323)
	at com.google.code.yanf4j.nio.impl.Reactor.run(Reactor.java:180)

错误的意思就是说 gets()方法调用是 无效的命令。如是网上查了一大堆就是没有解释这个错误是如何产生的，也没有说如何解决，可能是我搜索的方法不对，这个问题卡了好久，后来实在想不到就找了另外一台装有memcached的测试机测试，一下子通过了，如是把自己本机的memcached卸载掉重新把测试机上的版本拿过来装一遍，之后在测试也通过的，最后的问题症结在于： 当xmemcached版本是比较新的时候，memecached的版本也必须升级，必须是在memecached1.2.1以上的版本，新版的xmemcached在实现上有所改动，目前本地上我的是memecached1.4.4-14，xmemcached2.0.0