HELLO

Negotiates the protocol version and optionally authenticates the connection.

Syntax

HELLO protover [AUTH username password] [SETNAME clientname]

Parameters

Parameter	Type	Required	Description
`protover`	integer	Yes	Protocol version to use (`2` for RESP2, `3` for RESP3)
`AUTH username password`	string, string	No	Optional inline authentication
`SETNAME clientname`	string	No	Optional client connection name

Return Value

Returns connection metadata in a format determined by the negotiated protocol version:

RESP2: Array of alternating key-value pairs.
RESP3: Map.

Field	Type	Description
`server`	string	Server product name (`Kronotop`)
`version`	string	Server version
`proto`	integer	Negotiated protocol version
`id`	integer	Client connection ID
`mode`	string	Server mode (`cluster`)
`role`	string	Server role (`master`)
`modules`	array	Loaded modules (empty array)

Behavior

Sets the RESP protocol version for the current session. If AUTH is provided, authenticates the connection using the same logic as the AUTH command. If SETNAME is provided, sets the client connection name.

The protocol version is applied after the response is generated, so the response itself is encoded using the newly negotiated version.

This command does not require the cluster to be initialized.

Errors

Error	Condition
`NOPROTO`	Unsupported protocol version (not 2 or 3)
`WRONGPASS`	Invalid username or password in the AUTH clause

Examples

Switch to RESP3:

127.0.0.1:5484> HELLO 3
1# "server" => "Kronotop"
2# "version" => "0.13"
3# "proto" => (integer) 3
4# "id" => (integer) 1
5# "mode" => "cluster"
6# "role" => "master"
7# "modules" => (empty array)

Switch to RESP2 with authentication:

127.0.0.1:5484> HELLO 2 AUTH admin mysecretpassword
 1) "server"
 2) "Kronotop"
 3) "version"
 4) "0.13"
 5) "proto"
 6) (integer) 2
 7) "id"
 8) (integer) 1
 9) "mode"
10) "cluster"
11) "role"
12) "master"
13) "modules"
14) (empty array)

Set client name:

127.0.0.1:5484> HELLO 3 SETNAME my-app
1# "server" => "Kronotop"
2# "version" => "0.13"
3# "proto" => (integer) 3
4# "id" => (integer) 1
5# "mode" => "cluster"
6# "role" => "master"
7# "modules" => (empty array)