How to use the client-server API

Note

The git version of this document is 76ffe27

This guide focuses on how the client-server APIs provided by the reference homeserver can be used. Since this is specific to a homeserver implementation, there may be variations in relation to registering/logging in which are not covered in extensive detail in this guide.

If you haven't already, get a homeserver up and running on https://localhost:8448.

Accounts

Before you can send and receive messages, you must register for an account. If you already have an account, you must login into it.

Registration

The aim of registration is to get a user ID and access token which you will need when accessing other APIs:

curl -XPOST -d '{"username":"example", "password":"wordpass", "auth": {"type":"m.login.dummy"}}' "https://localhost:8448/_matrix/client/r0/register"

{
    "access_token": "QGV4YW1wbGU6bG9jYWxob3N0.AqdSzFmFYrLrTmteXc",
    "home_server": "localhost",
    "user_id": "@example:localhost"
}

NB: If a user is not specified, one will be randomly generated for you. If you do not specify a password, you will be unable to login to the account if you forget the access_token.

Implementation note: The matrix specification does not enforce how users register with a server. It just specifies the URL path and absolute minimum keys. The reference homeserver uses a username/password to authenticate user, but other homeservers may use different methods. This is why you need to specify the type of method.

Login

The aim when logging in is to get an access token for your existing user ID:

curl -XGET "https://localhost:8448/_matrix/client/r0/login"

{
    "flows": [
        {
            "type": "m.login.password"
        }
    ]
}

curl -XPOST -d '{"type":"m.login.password", "user":"example", "password":"wordpass"}' "https://localhost:8448/_matrix/client/r0/login"

{
    "access_token": "QGV4YW1wbGU6bG9jYWxob3N0.vRDLTgxefmKWQEtgGd",
    "home_server": "localhost",
    "user_id": "@example:localhost"
}

Implementation note: Different homeservers may implement different methods for logging in to an existing account. In order to check that you know how to login to this homeserver, you must perform a GET first and make sure you recognise the login type. If you do not know how to login, you can GET /login/fallback which will return a basic webpage which you can use to login. The reference homeserver implementation support username/password login, but other homeservers may support different login methods (e.g. OAuth2).

Communicating

In order to communicate with another user, you must create a room with that user and send a message to that room.

Creating a room

If you want to send a message to someone, you have to be in a room with them. To create a room:

curl -XPOST -d '{"room_alias_name":"tutorial"}' "https://localhost:8448/_matrix/client/r0/createRoom?access_token=YOUR_ACCESS_TOKEN"

{
    "room_alias": "#tutorial:localhost",
    "room_id": "!asfLdzLnOdGRkdPZWu:localhost"
}

The "room alias" is a human-readable string which can be shared with other users so they can join a room, rather than the room ID which is a randomly generated string. You can have multiple room aliases per room.

Sending messages

You can now send messages to this room:

curl -XPOST -d '{"msgtype":"m.text", "body":"hello"}' "https://localhost:8448/_matrix/client/r0/rooms/%21asfLdzLnOdGRkdPZWu:localhost/send/m.room.message?access_token=YOUR_ACCESS_TOKEN"

{
    "event_id": "YUwRidLecu"
}

The event ID returned is a unique ID which identifies this message.

NB: There are no limitations to the types of messages which can be exchanged. The only requirement is that "msgtype" is specified. The Matrix specification outlines the following standard types: m.text, m.image, m.audio, m.video, m.location, m.emote. See the specification for more information on these types.

Users and rooms

Each room can be configured to allow or disallow certain rules. In particular, these rules may specify if you require an invitation from someone already in the room in order to join the room. In addition, you may also be able to join a room via a room alias if one was set up.

Inviting a user to a room

You can directly invite a user to a room like so:

curl -XPOST -d '{"user_id":"@myfriend:localhost"}' "https://localhost:8448/_matrix/client/r0/rooms/%21asfLdzLnOdGRkdPZWu:localhost/invite?access_token=YOUR_ACCESS_TOKEN"

This informs @myfriend:localhost of the room ID !CvcvRuDYDzTOzfKKgh:localhost and allows them to join the room.

Joining a room via an invite

If you receive an invite, you can join the room:

curl -XPOST -d '{}' "https://localhost:8448/_matrix/client/r0/rooms/%21asfLdzLnOdGRkdPZWu:localhost/join?access_token=YOUR_ACCESS_TOKEN"

NB: Only the person invited (@myfriend:localhost) can change the membership state to "join". Repeatedly joining a room does nothing.

Joining a room via an alias

Alternatively, if you know the room alias for this room and the room config allows it, you can directly join a room via the alias:

curl -XPOST -d '{}' "https://localhost:8448/_matrix/client/r0/join/%21asfLdzLnOdGRkdPZWu:localhost?access_token=YOUR_ACCESS_TOKEN"

{
    "room_id": "!CvcvRuDYDzTOzfKKgh:localhost"
}

You will need to use the room ID when sending messages, not the room alias.

NB: If the room is configured to be an invite-only room, you will still require an invite in order to join the room even though you know the room alias. As a result, it is more common to see a room alias in relation to a public room, which do not require invitations.

Getting events

An event is some interesting piece of data that a client may be interested in. It can be a message in a room, a room invite, etc. There are many different ways of getting events, depending on what the client already knows.

Getting all state

If the client doesn't know any information on the rooms the user is invited/joined on, they can get all the user's state for all rooms:

curl -XGET "https://localhost:8448/_matrix/client/r0/sync?access_token=YOUR_ACCESS_TOKEN"

{
    "account_data": {
        "events": [
            {
                ...
            }
        ]
    },
    "next_batch": "s9_3_0_1_1_1",
    "presence": {
        "events": [
            {
                "content": {
                    "currently_active": true,
                    "last_active_ago": 19,
                    "presence": "online"
                },
                "sender": "@example:localhost",
                "type": "m.presence"
            }
        ]
    },
    "rooms": {
        "invite": {},
        "join": {
            "!asfLdzLnOdGRkdPZWu:localhost": {
                "account_data": {
                    "events": []
                },
                "ephemeral": {
                    "events": []
                },
                "state": {
                    "events": []
                },
                "timeline": {
                    "events": [
                        {
                            "content": {
                                "creator": "@example:localhost"
                            },
                            "event_id": "$14606534990LhqHt:localhost",
                            "origin_server_ts": 1460653499699,
                            "sender": "@example:localhost",
                            "state_key": "",
                            "type": "m.room.create",
                            "unsigned": {
                                "age": 239192
                            }
                        },
                        {
                            "content": {
                                "avatar_url": null,
                                "displayname": null,
                                "membership": "join"
                            },
                            "event_id": "$14606534991nsZKk:localhost",
                            "membership": "join",
                            "origin_server_ts": 1460653499727,
                            "sender": "@example:localhost",
                            "state_key": "@example:localhost",
                            "type": "m.room.member",
                            "unsigned": {
                                "age": 239164
                            }
                        },
                        ...
                    ],
                    "limited": false,
                    "prev_batch": "s9_3_0_1_1_1"
                },
                "unread_notifications": {}
            }
        },
        "leave": {}
    }
}

This returns all the room information the user is invited/joined on, as well as all of the presences relevant for these rooms. This can be a LOT of data. You may just want the most recent event for each room. This can be achieved by applying a filter that asks for a limit of 1 timeline event per room:

curl --globoff -XGET "https://localhost:8448/_matrix/client/r0/sync?filter={'room':{'timeline':{'limit':1}}}&access_token=YOUR_ACCESS_TOKEN"

{
    ...
    "rooms": {
        "invite": {},
        "join": {
            "!asfLdzLnOdGRkdPZWu:localhost": {
                ...
                "timeline": {
                    "events": [
                        {
                            "content": {
                                "body": "hello",
                                "msgtype": "m.text"
                            },
                            "event_id": "$14606535757KCGXo:localhost",
                            "origin_server_ts": 1460653575105,
                            "sender": "@example:localhost",
                            "type": "m.room.message",
                            "unsigned": {
                                "age": 800348
                            }
                        }
                    ],
                    "limited": true,
                    "prev_batch": "t8-8_7_0_1_1_1"
                },
                "unread_notifications": {}
            }
        },
        "leave": {}
    }
}

(additionally we have to ask curl not to try to interpret any {} characters in the URL, which is what the --globoff option is for)

Getting live state

In the response to this sync request the server includes a token that can be used to obtain updates since this point under the object key next_batch. To use this token, specify its value as the since parameter to another /sync request.:

curl -XGET "https://localhost:8448/_matrix/client/r0/sync?since=s9_7_0_1_1_1&access_token=YOUR_ACCESS_TOKEN"

{
    "account_data": {
        "events": []
    },
    "next_batch": "s9_9_0_1_1_1",
    "presence": {
        "events": [
            {
                "content": {
                    "currently_active": true,
                    "last_active_ago": 12,
                    "presence": "online"
                },
                "sender": "@example:localhost",
                "type": "m.presence"
            }
        ]
    },
    "rooms": {
        "invite": {},
        "join": {},
        "leave": {}
    }
}

By default this request will not wait in the server, always returning a value even if nothing interesting happened. However, by applying the timeout query parameter, which gives a duration in miliseconds, we can ask the server to wait for up to that amount of time before it returns. If no interesting events have happened since then, the response will be relatively empty.:

curl -XGET "https://localhost:8448/_matrix/client/r0/sync?since=s9_13_0_1_1_1&access_token=YOUR_ACCESS_TOKEN"
{
    "account_data": {
        "events": []
    },
    "next_batch": "s9_13_0_1_1_1",
    "presence": {
        "events": []
    },
    "rooms": {
        "invite": {},
        "join": {},
        "leave": {}
    }
}

Example application

The following example demonstrates registration and login, live event streaming, creating and joining rooms, sending messages, getting member lists and getting historical messages for a room. This covers most functionality of a messaging application.