-
The Redis protocol is a compromise between being easy to parse by a computer
+ = Protocol Specification =
The Redis protocol is a compromise between being easy to parse by a computer
and being easy to parse by an human. Before reading this section you are
strongly encouraged to read the "REDIS TUTORIAL" section of this README in order
-to get a first feeling of the protocol playing with it by TELNET.
A client connects to a Redis server creating a TCP connection to the port 6973.
+to get a first feeling of the protocol playing with it by TELNET.
A client connects to a Redis server creating a TCP connection to the port 6379.
Every redis command or data transmitted by the client and the server is
terminated by "\r\n" (CRLF).
The simplest commands are the inline commands. This is an example of a
server/client chat (the server chat starts with S:, the client chat with C:)
@@ -102,7 +102,30 @@ S: bar
starting with "+" terminated by "\r\n". For example:
+OK
The client library should return everything after the "+", that is, the string "OK" in the example.
The following commands reply with a status code reply:
-PING, SET, SELECT, SAVE, BGSAVE, SHUTDOWN, RENAME, LPUSH, RPUSH, LSET, LTRIMThis type of reply is just a CRLF terminated string representing an integer, prefixed by a ":" byte. For example ":0\r\n", or ":1000\r\n" are integer replies.
With commands like INCR or LASTSAVE using the integer reply to actually return a value there is no special meaning for the returned integer. It is just an incremental number for INCR, a UNIX time for LASTSAVE and so on.
Some commands like EXISTS will return 1 for true and 0 for false.
Other commands like SADD, SREM and SETNX will return 1 if the operation was actually done, 0 otherwise.
The following commands will reply with an integer reply: SETNX, DEL, EXISTS, INCR, INCRBY, DECR, DECRBY, DBSIZE, LASTSAVE, RENAMENX, MOVE, LLEN, SADD, SREM, SISMEMBER, SCARDA client can use the same connection in order to issue multiple commands.
+PING, SET, SELECT, SAVE, BGSAVE, SHUTDOWN, RENAME, LPUSH, RPUSH, LSET, LTRIMThis type of reply is just a CRLF terminated string representing an integer, prefixed by a ":" byte. For example ":0\r\n", or ":1000\r\n" are integer replies.
With commands like INCR or LASTSAVE using the integer reply to actually return a value there is no special meaning for the returned integer. It is just an incremental number for INCR, a UNIX time for LASTSAVE and so on.
Some commands like EXISTS will return 1 for true and 0 for false.
Other commands like SADD, SREM and SETNX will return 1 if the operation was actually done, 0 otherwise.
The following commands will reply with an integer reply: SETNX, DEL, EXISTS, INCR, INCRBY, DECR, DECRBY, DBSIZE, LASTSAVE, RENAMENX, MOVE, LLEN, SADD, SREM, SISMEMBER, SCARDAs you can see with the protocol described so far there is no way to
+send multiple binary-safe arguments to a command. With bulk commands the
+last argument is binary safe, but there are commands where multiple binary-safe
+commands are needed, like the MSET command that is able to SET multiple keys
+in a single operation.
In order to address this problem Redis 1.1 introduced a new way of seding
+commands to a Redis server, that uses exactly the same protocol of the
+multi bulk replies. For instance the following is a SET command using the
+normal bulk protocol:
+SET mykey 8
+myvalue
+
While the following uses the multi bulk command protocol:
+*3
+$3
+SET
+$5
+mykey
+$8
+myvalue
+
Commands sent in this format are longer, so currently they are used only in
+order to transmit commands containing multiple binary-safe arguments, but
+actually this protocol can be used to send every kind of command, without to
+know if it's an inline, bulk or multi-bulk command.
It is possible that in the future Redis will support only this format.
A good client library may implement unknown commands using this
+command format in order to support new commands out of the box without
+modifications.A client can use the same connection in order to issue multiple commands.
Pipelining is supported so multiple commands can be sent with a single
write operation by the client, it is not needed to read the server reply
in order to issue the next command. All the replies can be read at the end.
Usually Redis server and client will have a very fast link so this is not