tcp nio 服务端、客户端例子--参考《分布式Java应用：基础与实践》

参考《分布式java应用》tcp nio 服务端、客户端例子， 在基础主要做了以下调整：

1. 信息长度由定长（ByteBuffer长度）修正为可变长（即不再收长度限制）

2. 特殊错误处理：read Exception，opposite close Exception，select timeout Exception（网络超时）。

read Exception 与 opposite close Exception 的处理， 用于解决发现异常后造成程序的 while死循环。

select timeout Exception的处理， 用于对网络超时的支持

-the tcp the nio service side, client examples- refer to distributed Java applications: Basis and Practice of " reference"　distributed java applications " tcp nio services, client, example, is based primarily on the following adjustments: 1. message length fixed-length (length of the ByteBuffer) correction is a variable length (ie, no longer received length limit) 2. special error handling: read the Exception, opposite the close the Exception, select timeout Exception (network timeout). the read the Exception, and opposite the close Exception handling is used to resolve discovered anomalies resulting from the program while infinite loop. select timeout of Exception handling, for the support of the network timeout