在官方网站http://redis.io/topics/protocol我们必须redis通信协议做说明。
根据以下某些原因。我想解决redis client protocol：
1、足够了解通信协议。有助于做出更好的系统设计。
2、学习RESP的设计思想，不仅能扩展我的思维，或许将来能应用于我的代码中。
3、由于有些人想将redis client直接并入自己已有的系统中；包含我在内。这个将在我以后的文章再做说明。
以下我翻译一下http://redis.io/topics/protocol一些我觉得重要的内容：
Redis clients communicate with the Redis server using a protocol called RESP (REdis Serialization Protocol). While the protocol was designed specifically for Redis, it can be used for other client-server software projects.
RESP is a compromise between the following things:
- Simple to implement.
- Fast to parse.
- Human readable.
RESP can serialize different data types like integers, strings, arrays. There is also a specific type for errors. Requests are sent from the client to the Redis server as arrays of strings representing the arguments of the command to execute. Redis replies with a command-specific data type.
RESP is binary-safe and does not require processing of bulk data transferred from one process to another, because it uses prefixed-length to transfer bulk data.
Note: the protocol outlined here is only used for client-server communication. Redis Cluster uses a different binary protocol in order to exchange messages between nodes.
译：
redisclient和redis服务端用一种名叫RESP(REdis Serialization Protocol)的协议通信。尽管这样的协议专门为redis设计，可是它能被用于其他基于C/S模型的软件项目中。
RESP是基于以下一些事实的一种折衷方案：
- 易于实现
- 高速解释
- 人类可读
RESP能序列化不同的数据类型。比如整型，字符串，数组，还有专门的错误类型。
client发送字符串数组请求到服务端。而字符串数组表示命令參数去运行。Redis会用专门的命令类型回复。
RESP是二进制安全的，同一时候过程转换中不须要大量的数据处理,由于它使用了前缀长度去转换批量数据。
注意：在这里概述的协议仅仅用于client-服务端通信。而Redis集群为了不同节点交换消息使用了一种不同的二进制协议。
RESP is actually a serialization protocol that supports the following data types: Simple Strings, Errors, Integers, Bulk Strings and Arrays.
The way RESP is used in Redis as a request-response protocol is the following:
- Clients send commands to a Redis server as a RESP Array of Bulk Strings.
- The server replies with one of the RESP types according to the command implementation.
In RESP, the type of some data depends on the first byte:
- For Simple Strings the first byte of the reply is "+"
- For Errors the first byte of the reply is "-"
- For Integers the first byte of the reply is ":"
- For Bulk Strings the first byte of the reply is "$"
- For Arrays the first byte of the reply is "
*"
Additionally RESP is able to represent a Null value using a special variation of Bulk Strings or Array as specified later.
In RESP different parts of the protocol are always terminated with " " (CRLF).
译：
RESP实际上是一种支持以下数据类型的序列化协议：短字符串。错误。整数，长字符串和数组。
RESP作为一种请求-回应协议。在Redis中的用法例如以下：
- client发送一种宛如RESP中长字符串数组的命令到Redis服务端。
- Redis服务端依据命令实现回复当中一种RESP类型。
在RESP中，一种数据类型基于第一个字节：
- 对于短字符串，回复的第一个字节是"+"
- 对于错误，回复的第一个字节是"-"
- 对于整数，回复的第一个字节是":"
- 对于长字符串，回复的第一个字节是"$"
- 对于数组，回复的第一个字节是"*"
在RESP中，协议的不同部分总是以" "(CRLF)作为结束。
前面说到的协议，我有强调了是client，就是说server回复client请求时用到的协议；client请求server时，仅仅须要在命令后面加上" "。
以下是5种类型的返回实例：
如果在redis server中存在下面键值对： name1 cat age1 10 短字符串 "set name2 fish " "+OK " 错误 "seet name3 dog " "-ERR unknown command 'seet' " 整数 "incr age1 " ":11 " 长字符串 ① "get name1 " "$3 cat " ② "get name3 " "$-1 " 数组 ① "mget name1 age1 " "*2 $3 cat $2 11 " ② "mget name2 age2 " "*2 $4 fish $-1 " ③ 其他情况会返回"*-1 "和"*0 ",详细参考redis官方文件;
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