Callback on message not sent yet

Description

After setting this callback, when a user sends a message to a one-on-one chat, group chat or room chat, In-app Chat will initiate a request to your business server, and you can perform real-time operations on the message through the response, such as:

Recording chat messages and intercepting requests for inappropriate speech;
Implementing black and white list functions to determine which messages can be sent normally.

Warning

The supported message types for this callback are text messages, image messages, file messages, audio messages, video messages, and custom messages. command messages and barrage messages are not supported.
This callback only supports messages sent via the client SDK. If messages are sent through the server, your business backend will not receive this callback.

Based on the value of the response from your business server, you can make one of the following four judgments on whether to send the message:

Value	Judgment	Whether to send the message	Result returned to the message sender	Whether the message recipient can receive the message
0	Neutral (not judged whether to send)	Send	Sent	Receivable
1	Send	Send	Sent	Receivable
2	Silently send	Send	Sent	Not receivable
3	Do not send	Do not send	Not sent	Not receivable

Callback request

Request method: POST/JSON

Note

The callback data needs to be decoded by UrlDecode.
When using the POST request method to pass parameters:
- The parameters in the body can be directly passed in the JsonObject format, without the need to serialize them into a string format.
- In the headers, set "Content-type" to "application/json".

Request endpoint: Contact ZEGOCLOUD Technical Support to configure the corresponding callback endpoint.
Transmission protocol: HTTPS/HTTP (HTTPS is recommended.)

Request parameters

Public parameters	Type	Description
appid	String	A unique identifier for the App.
event	String	Callback event, the return value of this callback is `before_send_msg`.
nonce	String	Random number, used to calculate signature.
signature	String	The verification string, see Authenticating server-to-server callbacks for details.
timestamp	Int	The current server time in Unix timestamp format, in seconds, used to calculate the signature.
request_id	String	Request ID.
Business parameters	Type	Description
from_user_id	String	Message sender ID.
conv_id	String	Target session ID.
conv_type	Int	Target session type: 0: One-on-one chat. 1: Room chat. 2: Group chat.
msg_id	String	Message ID, which can be used to determine the uniqueness of the message.
payload	String	Extra field.
msg_type	Int	Message type: 1: Text. 11: Images. 12: File. 13: Audio. 14: Video. 200: Custom.
sub_msg_type	Int	The specific custom type. The value is filled in when the user sends a custom message, and the value range is [0,200]. This parameter is meaningful only when msg_type is 200 (custom type).
msg_body	String	Message content. When msg_type is 1 (text type) or 200 (custom type), msg_body is the message content passed in when sending a message, and you can directly read the message content. When msg_type is 11, 12, 13, 14, that is, when the message is a media type, msg_body is a JSON string. Please use URLDecode to decode this JSON string, and parse this JSON string according to the multimedia message structure, and then obtain each field data in the message.

Note

We recommend that you convert some parameters to Int for logical processing. The relevant fields include appid and nonce.

msg_body JSON string parsing result parameter description

Parameters	Type	Description
md5	String	The MD5 value of the file.
file_name	String	File name.
file_size	String	File size in bytes.
download_url	String	Download URL.
media_duration	String	Audio and Video duration, in seconds.

Callback example

Untitled

{
    "appid": "1",
    "event": "before_send_msg",
    "from_user_id": "sender",
    "conv_id": "receiver",
    "request_id": "3501907290370176",
    "msg_id": "1234232421343",
    "conv_type": 0,
    "timestamp": 1499676968,
    "msg_body": "msg_body",
    "msg_type": 1,
    "signature": "abc",
    "nonce": "321",
    "sub_msg_type": 0,
    "payload": "payload"
}

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Response parameters

Parameters	Type	Description
result	Int	The value of your business server response to determine whether to send the message. 0: neutral (do not judge whether to send). 1: Send. 2: Push silently. 3: Do not send. Others: default to be neutral.

Sample response

Untitled

{
    "result": 0
}

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Return response

Returning an HTTP status code of 2XX (e.g., 200) indicates success, and other responses indicate failure.

Retry mechanism

If the ZEGOCLOUD server does not receive a response, it will retry after 3 seconds. If the callback fails after the second retry, it will no longer be retried and an exception is judged.

Note

When the ZEGOCLOUD client initiates a request to you, if an exception occurs on your business server, no message will be sent by default. If you want to send messages by default, contact ZEGOCLOUD Technical Support.