IMP 即时通信协议

概述

IMP 是基于 TCP 协议实现的即时通讯协议, 参考了 MSN 和 SLCK. 此协议仅用于计算机网络的学习, 不具备生产可用性.

支持的命令

ID	发送者	描述
REG	客户端	客户端注册
CHNS	客户端	列出所有的频道
JOIN	客户端	加入某个频道(没有则创建)
LEAVE	客户端	离开某个频道
MSG	客户端和服务端	发送或接收频道的消息
OK	客户端和服务端	命令确认
ERR	客户端和服务端	错误

接下来依次解释每个命令:

REG

When a client connects to a server, they can register as a client using the REG command. It takes an identifier as an argument, which is the client's username.

Syntax:

REG <handle>

where:

• handle: name of the user

JOIN

When a client connects to a server, they can join a channel using the JOIN command. It takes an identifier as an argument, which is the channel ID.

Syntax:

JOIN <channel-id>

where:

• channel-id: ID of the channel

LEAVE

Once a user has joined a channel, they can leave the channel using the LEAVE command, with the channel ID as argument.

Syntax:

LEAVE <channel-id>

where:

• channel-id: ID of the channel

Example 1: to leave the #general channel, the client can send:

LEAVE #general

MSG

To send a message to a channel or a user, the client can use the MSG command, with the channel or user identifier as argument, followed with the body length and the body itself.

Syntax:

MSG <entity-type> <entity-id> <length>\r\n[payload]

where:

• entity-id: the ID of the channel or user
• length: payload length
• payload: the message body

Example 1: send a Hello everyone! message to the #general channel:

MSG CHN general 16\r\nHello everyone!

Example 2: send a Hello! message to @jane:

MSG USER jane 4\r\nHey!

CHNS

To list all available channels, the client can send the CHNS message. The server will reply with the list of available channels.

Syntax:

CHNS

USERS

To list all users in a channel, the client can send the USERS message. The server will reply with the list of available users.

Syntax:

USERS <channel-id>

OK/ERR

When the server receives a command, it can reply with OK or ERR.

OK does not have any text after that, think of it as an HTTP 204.

ERR <error-message> is the format of the errors returned by the server to the client. No protocol errors result in the server closing the connection. That means that although an ERR has been returned, the server is still maintaining the connection with the client.

Example 1: Protocol error due to bad username selected during registration:

ERR Username must begin with @

Example 2: Protocol error due to bad channel ID sent with JOIN:

ERR Channel ID must begin with #