LEMP (Light Extensible Messaging Protocol) Server

LEMP is a new insfrastructure for instant messaging. Its packet format is based on JSON. It can be thought as a lighter alternative to XMPP (Extensible Messaging and Presence Protocol). It does not have any pretensions to be alternative of SIP, MQTT, AMQP vs. It defines its packet formats for its purposes. It is not a transport protocol indeed.

Presence of a client is determined by its authentication. No packet formats exist for controlling presence as in XMPP. If a client is authenticated to server then it is considered as "online". Store-Forward mechanism exists for messages of offline members. The messages sent to offline members are stored and they are forwarded to the client when it authenticates.

This project is a Java implementation of LEMP server. The server is implemeted to have websocket interface for packet flow. It uses Cassandra as the persistence layer and Apache Ignite as the cache layer.

There are 3 main datum types in LEMP.

1. Request
2. Information
3. Message

1. REQUEST

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Every request, except logout requests must have a response (Success or Error covered in section 1.9)

A response may have a content or may be empty (only success or error)

1.1. Authentication Request/Response

1.1.1 Login Request

An authentication request is sent to the server after the persistence network connection is setup.

Type	Packet
Request	{ rq:{id:"id",a:{i:"identity",t:"token"}} }
Response	{ rp:{id:"id", response:0/1} }

1.1.2 Logout Request

Type	Packet
Request	{ rq:{id:"id", lo:{r:"reason"}} }

1.2. User Followings Requests

1.2.1. Add Followings Request

Type	Packet
Request	{ rq:{id:"id", af:[{u:"f1",n:"nick1"},{u:"f2",n:"nick2"},{u:"f2",n:"nick2"}]} }

1.2.2. Remove Following Request

Type	Packet
Request	{ rq:{id:"id", rf:["f1","f2"]} }

1.2.3. Update Following Request

Type	Packet
Request	{ rq:{id:"id", uf:[{u:"f1",n:"nick1"},{u:"f2",n:"nick2"},{u:"f2",n:"nick2"}]} }

1.3. State (Last Offline) Request/Response

Type	Packet
Request	{ rq:{id:"id", s:{u:"username"}} }
Response	{ rp:{id:"id", s:{u:"username", v:"0/unixtime"}} }

1.4. Personal Requests

1.4.1. Picture Set Request

Type	Packet
Request	{ rq:{id:"id", p:{t:"s", v:"picUrl"}} }

1.4.2. Picture Get Request/Response

Type	Packet
Request	{ rq:{id:"id", p:{t:"g", u:"username"}} }
Response	{ rp:{id:"id", p:{u:"username", v:"picUrl"}} }

1.4.3. Status Set Request

Type	Packet
Request	{ rq:{id:"id", st:{t:"s", s:"status"}} }

1.4.4. Status Get Request/Response

Type	Packet
Request	{ rq:{id:"id", st:{t:"g", u:"username"}} }
Response	{ rp:{id:"id", st:{u:"username", s:"status"}} }

1.5. Privacy Requests

1.5.1. Block Request

Type	Packet
Request	{ rq:{id:"id", b:{u:"username"}} }

1.5.2. Unblock Request

Type	Packet
Request	{ rq:{id:"id", ub:{u:"username"}} }

1.5.3. Get Privacy List Request

Type	Packet
Request	{ rq:{id:"id", get:{o:"pr"}} }
Response	{ rp:{id:"id", pr:["user1","user2","user"3]} }

1.6. Group Requests

1.6.1. Create Group Request

Type	Packet
Request	{ rq:{id:"id", g:{t:"c", i:"id",n:"groupname", p:"picture", m:["member1", "member2", "member3"]}}}

1.6.2. Add Users to Group Request

Type	Packet
Request	{ rq:{id:"id", g:{t:"a", i:"id",m:["member1", "member2", "member3"]}}}

1.6.3. Banish Users from Group Request

Type	Packet
Request	{ rq:{id:"id", g:{t:"b",i:"id",m:["member1", "member2", "member3"]}}}

1.6.4. Leave from Group Request

Type	Packet
Request	{ rq:{id:"id", g:{t:"l", i:"id"}}}

1.6.5. Terminate Group Request

Type	Packet
Request	{ rq:{id:"id", g:{t:"t", i:"id"}}}

1.6.6. Group Information Request/Response

Type	Packet
Request	{ rq:{id:"id", g:{t:"i", i:"id"}}}
Response	{ rp:{id:"id", g:{i:"id",c:"creationdate",mt:"mutetill",m:["member1", "member2","member3"]}} }

1.6.7. Admins Add Request

Type	Packet
Request	{ rq:{id:"id", g:{t:"aad", i:"id", ad:["member1","member2"]}}}

1.6.8. Admins Get Request/Response

Type	Packet
Request	{ rq:{id:"id", g:{t:"ad", i:"id"}}}
Response	{ rp:{id:"id", g:{i:"id",ad:["member1", "member2","member3"]}} }

1.6.9. Picture Set Request

Type	Packet
Request	{ rq:{id:"id", p:{t:"s", i:"id", v:"base64value"}} }

1.6.10. Picture Get Request/Response

Type	Packet
Request	{ rq:{id:"id", p:{t:"g", i:"id"}} }
Response	{ rp:{id:"id", p:{i:"id", v:"base64value"}} }

1.6.11. Name Set Request

Type	Packet
Request	{ rq:{id:"id", n:{t:"s", i:"id", n:"name"}} }

1.6.12. Name Get Request/Response

Type	Packet
Request	{ rq:{id:"id", n:{t:"g", i:"id"}} }
Response	{ rp:{id:"id", n:{i:"id", n:"groupname"}} }

1.6.13. Mute Request

Type	Packet
Request	{ rq:{id:"id", mt:{i:"id",t:"mutetill"}} }

1.6.14. Unmute Request

Type	Packet
Request	{ rq:{id:"id", umt:{i:"id"}} }

1.7. Broadcast Group Requests

1.7.1. Create Broadcast Group Request

Type	Packet
Request	{ rq:{id:"id", br:{t:"c", i:"id",n:"broadcastname", p:"picture", m:["member1", "member2", "member3"]}}}

1.7.2. Add Users to Broadcast Group Request

Type	Packet
Request	{ rq:{id:"id", br:{t:"a", i:"id",m:["member1", "member2", "member3"]}}}

1.7.3. Banish Users from Broadcast Group Request

Type	Packet
Request	{ rq:{id:"id", br:{t:"b",i:"id",m:["member1", "member2", "member3"]}}}

1.7.4. Terminate Broadcast Group Request

Type	Packet
Request	{ rq:{id:"id", br:{t:"t", i:"id"}}}

1.7.5. Broadcast Group Information Request/Response

Type	Packet
Request	{ rq:{id:"id", br:{t:"i", i:"id"}}}
Response	{ rp:{id:"id", br:{i:"id",c:"creationdate",n:"name",m:["member1", "member2","member3"]}} }

1.7.6. Picture Set Request

Type	Packet
Request	{ rq:{id:"id", p:{t:"s", b:"id", v:"base64value"}} }

1.7.7. Picture Get Request/Response

Type	Packet
Request	{ rq:{id:"id", p:{t:"g", b:"id"}} }
Response	{ rp:{id:"id", p:{b:"id", v:"base64value"}} }

1.7.8. Name Set Request

Type	Packet
Request	{ rq:{id:"id", n:{t:"s", b:"id", n:"name"}} }

1.7.9. Name Get Request/Response

Type	Packet
Request	{ rq:{id:"id", n:{t:"g", b:"id"}} }
Response	{ rp:{id:"id", n:{b:"id", n:"broadcastname"}} }

1.8. Server Requests

1.8.1. Server Time Request/Response

Type	Packet
Request	{srq:{id:"id",t:"t"}}
Response	{ srp:{id:"id", t:"t", tm:"serverunixtime"}, o:-2 }

1.8.2. Knock-Knock Request

Type	Packet
Request	{srq:{id:"id",t:"k"}}
Response	{ srp:{id:"id", t:"k"} }

1.9. Response/Error

Id of the response must be same as the id of the request.

1.9.1. Successful Response

Type	Packet
Response	{ rp:{id:"id"} }

1.9.2. Erroneous Response

Type	Packet
Response	{ rp:{id:"id", e:{c:"code",d:"description"}} }

1.10. Admin Requests

1.10.1. Create New User Request

Type	Packet
Request	{ rq:{id:"id", ad:{c:"cr/del", i:"identity", t:"token", ty:"0/1"}}}

• Commands (c)

  • cr : create
  • del: delete

• User Types (ty)

  • 0: user
  • 1: admin

2. INFORMATION

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2.1. Login/Logout info broadcast to followers

2.1.1. Login Information Broadcast

Type	Packet
Info	{ i:{id:"id", li:"username"} }

2.1.2. Logout Information Broadcast

Type	Packet
Info	{ i:{id:"id", lo:"username"} }

2.2. Group Information Broadcast

2.2.1. Group created info

Type	Packet
Info	{ i:{id:"id", g:{t:"c",i:"id",n:"name"} } }

2.2.2. Group member added info

Type	Packet
Info	{ i:{id:"id", g:{t:"a",i:"id",m:["member1", "member2", "member3"]} } }

2.2.3. Group user banished info

Type	Packet
Info	{ i:{id:"id", g:{t:"b",i:"id",m:"member1"} } }

2.2.4. Group terminated info

Type	Packet
Info	{ i:{id:"id", g:{t:"t"} } }

2.2.5. Group picture changed info

Type	Packet
Info	{ i:{id:"id", g:{t:"p"} } }

2.2.6. Group name changed info

Type	Packet
Info	{ i:{id:"id", g:{t:"n"} } }

3. MESSAGE

---

Type	Packet
Message	{ m:{id:"id", s:"sender", r:"receiver", t:"t/p/v/a/l", c:"content", st:sent_time, p:"0/1", sc:"0/1", pc:"0/1"} }

• Message Types (t)

  • t: text
  • p: photo
  • v: video
  • a: audio
  • l: location

• Persistency (p)

  • 0: do not persist if the receiver is offline
  • 1: persist the message if the receiver is offline (default)

• Server Receipt (sc)

  • 0: the server does not sent message received message
  • 1: the server sents message received message (default)

• Peer Receipt (pc)

  • 0: the peer does not sent message received message
  • 1: the peer sents message received message (default)

3.1. Server Receipt Message

Server receipt message is sent for all messages delivered to the server.

Type	Packet
Message	{ m:{id:"id", sr:{id:"sent_messageId"} } }

3.2. Delivered Message

Type	Packet
Message	{ m:{id:"id", st:sent_time, dm:{id:"received_messageId"} } }

3.3. Noticed Message

Type	Packet
Message	{ m:{id:"id", st:sent_time, nm:{id:"noticed_messageId"} } }