1. socket通信：有客户端和服务端的socket代码。



2. 多线程：客户端和服务端各用一线程发送信息；服务端另有一监听线程，用于把超时的信息删除。



这里应用到了同步，使两个线程可以操作同一个map。 -1. Socket communications: There are client and service side of the socket code. 2. Multi-threading: client and server uses one thread to send messages　service client and another one monitor thread, used to delete overtime information. Here applied to synchronize the two threads can operate with a map.