RocketMQ的MQClientException

我运行了RocketMQ的Producer样例，运行一段时间后会出现下面的异常，请问是什么原因呢？

PaymentMessage{orderId=1465799354525, payAmount=24303.0, paySource=0, payPlatform=0, createTime=1465799420280}
com.alibaba.rocketmq.client.exception.MQClientException: wait response timeout 3000ms
For more information, please visit the url, https ://github.com/alibaba/RocketMQ/issues/48
    at com.alibaba.rocketmq.client.impl.MQClientAPIImpl$1.operationComplete(MQClientAPIImpl.java:344)
    at com.alibaba.rocketmq.remoting.netty.ResponseFuture.executeInvokeCallback(ResponseFuture.java:62)
    at com.alibaba.rocketmq.remoting.netty.NettyRemotingAbstract.scanResponseTable(NettyRemotingAbstract.java:331)
    at com.alibaba.rocketmq.remoting.netty.NettyRemotingClient$5.run(NettyRemotingClient.java:309)
    at java.util.TimerThread.mainLoop(Timer.java:555)
    at java.util.TimerThread.run(Timer.java:505)