Group members can send and receive messages in a group, which is similar to the chat mode of QQ and WeChat groups.
The app admin can send messages from the backend or simulate users to send messages. In the latter case, even if the app admin or sender is not a group member, the messages will still be delivered.
The app admin can send system messages from the backend. These messages are delivered as system messages to specified online group members, and the app admin’s custom messages that are received on the app can be handled in special ways.
Instant Messaging (IM) maintains a message SEQ for each group, which starts from 1. Every time an ordinary message is sent in the group chat, the IM backend uses the current SEQ value as the SEQ of the message and then increases the SEQ by 1.
Group ID and SEQ together constitute the unique identifier of a message.
IM generates incremental SEQs only for messages that are subject to roaming storage.
|Text||The message content is plain text.|
|Image||The message content includes the URL, dimensions, and size of the image.|
|Emoji||Emoji messages are customized by developers.|
|Audio||Audio data must include the duration in seconds.|
|Location||The message content includes the caption, longitude, and latitude of the location.|
|File||The message content includes the URL, size, and format of the file. There are no file format restrictions, and the maximum supported file size is 100 MB.|
|Short video||The message content includes the URL, duration, size, and format of the short video file. The maximum file size supported is 100 MB.|
|Custom||Message types that are customized by developers, such as red packet and rock-paper-scissor.|
|System notification||This type of message includes built-in system notification messages and system notification messages customized by developers.|
|Type||Feature Description||Application Scenario|
|Send ordinary group messages||Group members can send messages through the IM SDK APIs. By calling RESTful APIs, app admins can send messages in any group without joining the group.||Group members send messages in the group, and app admins can send messages in any group.|
|Send group system messages||By calling RESTful APIs, app admins can send system messages in any group without joining the group. These system messages are only received by online group members and do not possess roaming capabilities.||App admins push time-sensitive notifications to all or some of online group members.|
|Offline push of group messages||Supported by Apple, Huawei, Xiaomi, OPPO, Vivo, and Meizu mobile phones||Offline push of group chat messages|
|Receive online group messages||Group members can receive online group messages through the IM SDK.||Online group members receive group messages in real time.|
|Group members receive offline messages or historical messages||Group members can query historical messages through the IM SDK.||Group members receive offline messages when they go back online, and group members can view group chat history.|
|App backend obtains group messages||App admins can download all messages generated during a certain time period through RESTful APIs. App admins can also obtain the chat history of any group through RESTful APIs. The app backend can obtain group messages through callback after messages are sent in the group.||Back up message history regularly. Obtain message history of specific groups. Obtain group messages in real time.|
|Delete messages||Historical messages can be deleted through RESTful APIs to ensure that they will not be further propagated.||Delete malicious information in a group.|
|Group messages carry sender profiles||Group messages can contain the sender nickname, profile photo, group name card, user-level custom fields, and member-level custom fields.||Display sender information such as the nickname and profile photo.|
|Group message sending control||You can control group message sending by muting and callback before delivering group messages.||Prevent a group member from sending messages, prevent all group members from sending messages, and filter or modify messages at the app backend.|
|Group message receiving control||You can set different message receiving options for individual groups: receive and notify, receive without notifying, and block messages. When receive without notifying is selected, iOS devices will disable APNs.||Block messages from a group.|
|Group message frequency control||Manage the sending frequency of ordinary group messages. The default value is 40 messages per second. Group system messages sent by the app admin through RESTful APIs are not subject to frequency control. For more information, see Message Priority and Frequency Control described below.||Prevent spam messages.|
If the sender nickname and profile photo need to be included, the information in these two fields must be imported to user profiles in IM.
If custom fields need to be included, configure custom fields in the console and submit a ticket to add the corresponding fields to messages.
The sending of group messages can be managed through the following methods:
|Mute group members||Prevent a group member from sending messages for a certain period of time. This feature is effective within a single group. If the muted user leaves the group and joins again, the user remains muted until the mute time expires.|
|Callback before delivering group messages||Before delivering a message to group members, IM checks with the app backend for permission. If not allowed, the message will not be delivered.
After receiving a callback, the app backend can modify the message content and return it to IM, which will deliver the modified message. For more information, see Callback Before Delivering Group Messages.
After initiating a callback, IM will deliver the message directly if it does not receive a response in 2 seconds, without retrying.
Group messages are divided into three levels by priority. If a group exceeds the message frequency limit, the backend delivers high-priority messages first. Therefore, select appropriate priorities according to the importance of messages.
The following lists the priorities from high to low:
|Priority||Recommended Message Type|
|High||Red packet and prize message|
|Normal||Plain text message|
Number-based frequency control limits the maximum number of messages sent per second in a single group. The default value is 40 messages per second. When the number of sent messages exceeds the limit, the backend will first deliver higher-priority messages, with messages of same priority delivered randomly.
A message that has been restricted by frequency control is not delivered or stored in the message history, but a success response will be returned to the sender. Callback before delivering group message is triggered, but callback after delivering group message is not triggered.
Priority-based frequency control limits the maximum number of messages with a certain priority sent per second in a single group. A message sending request must first pass the number-based frequency control check before it enters the priority-based frequency control processing.
All messages are subject to the frequency limit of 40 messages per second. You can set 3 levels of priority. Messages with High priority are the top-priority messages, which are not likely to be restricted. However, if the number of high-priority messages sent in a second exceeds 40, high-priority messages will also be discarded.
sendMessageto send messages to group C when user B is offline.
loginAPI to log in to IM.
OnRefreshAPI when group message synchronization is completed.
getMessage, and the SDK automatically pulls the messages from the roaming server.